Enzyme and Microbial Technology41(2007)
570–575
Characteristic of?-glucosidase from Sicilian blood
oranges in relation to anthocyanin degradation
R.N.Barbagallo a,?,R.Palmeri a,S.Fabiano a,P.Rapisarda b,G.Spagna a,?
a Dipartimento di Orto?oroArboricoltura e Tecnologie Agroalimentari(DOFATA),Via Santa So?a98,951123Catania,Italy
b CRA-Istituto Sperimentale per l’Agrumicoltura,Corso Savoia190,95024Acireale(CT),Italy
Received5August2005;received in revised form9May2007;accepted9May2007
Abstract
Anthocyanin content in Sicilian sweet orange[Citrus sinensis(L)Osbeck]varieties known as blood oranges(Tarocco,Moro e Sanguinello) undergoes changes during the ripening process.Concentration increases during ripening,reaching a maximum in the fully ripe fruit.At latter stage of maturity,a decrease of these pigments is observed.This study aims to evaluate?-d-glucosidase activity(?G,EC3.2.1.21)in Tarocco variety, the most common Sicilian blood orange,and to determine the main physicochemical and kinetic properties of this enzyme in order to underline its role on anthocyanins degradation during ripening.The enzymatic extract was assayed on both anthocyanins extract from Tarocco juice and a synthetic substrate(p-nitrophenyl-?-d-glucopyranoside,p NPG).It was observed a400times higher speci?city of the synthetic substrate than the natural substrate.Kinetic studies and physicochemical characterization of?G such as V max and K m(V max2.1×10?2and K m2.67×10?4using p NPG as substrate;V max3.3×10?3and K m2.1×10?1using natural substrate),optimum conditions of pH(4.5)and temperature(60?C),fructose and glucose inhibition(competitive inhibition by glucose)and thermal stability(decimal reduction time3min at75?C and decimal reduction temperature9.5?C)were also performed.?-d-Glucosidase activity seems involved on anthocyanins degradation during?nal ripening stage of fruit.?2007Elsevier Inc.All rights reserved.
Keywords:Tarocco orange;?-d-Glucosidase;Anthocyanins;Stability;Ripening
1.Introduction
Citrus fruit are important sources of health promoting con-stituents.In addition to ascorbic acid,these include?avonoids, hydroxycinnamic acids,carotenoids and limonoids[1].Some of these compounds are present as glycosides and the type and position of glycosidic substituent has a profound effect on taste,solubility and bioavailability.Anthocyanins are glycosides belonging to the?avonoid compounds,a class of plant secondary metabolites responsible for the rind and?esh red color of some Sicilian sweet orange[Citrus sinensis(L)Osbeck]varieties known as blood oranges(Tarocco,Moro e Sanguinello).Antho-cyanin content has been considered as an important quality attribute in both fresh fruit market and processing industry due to its biological activity[2,3].Several anthocyanins have been ?Corresponding author at:Food Biotechnology Group,DOFATA,University of Catania,Via S.So?a98,95123Catania,Italy.Tel.:+390957580213; fax:+390957141960.
E-mail addresses:rbarbaga@unict.it(R.N.Barbagallo),
gspagna@unict.it(G.Spagna).identi?ed in blood oranges juice,with cyanidin-3-glucoside and cyanidin-3-(6 -malonyl)-glucoside as the major pigments [4,5].
Anthocyanins stability in fruit is promoted by copigmenta-tion with other?avonoids or phenolic acids,self-association, and low pH[6].On the other hand,enzymatic systems present in plant tissues such as anthocyanase(anthocyanin-?-glucosidase) and polyphenoloxidase could play an important role in degrada-tion process of anthocyanins.Such enzymes mainly act during senescence of fruit,hydrolising and oxidizing the anthocyanin molecules.Few works have been carried out on citrus fruit?-glycosidase(?G).Burns[7]found a low level of?-glycosidase activity in sweet orange fruit juice vesicles,while no activity of this enzyme was detected in grapefruit peel and juice vesicle [8–10].Finally,a recent study[11]put in evidence the pres-ence of?G in fruit?avedo and albedo tissue of Valencia orange variety.Despite the importance of?-d-glucosidase(?G,EC 3.2.1.21)activity on?avour pro?le of many fruit,few researches were found about its role on anthocyanins degradation.Due to loss of glycosidic moiety for hydrolysis,the aglycon(antho-cyanidin)could become extremely unstable with consequent
0141-0229/$–see front matter?2007Elsevier Inc.All rights reserved. doi:10.1016/j.enzmictec.2007.05.006
R.N.Barbagallo et al./Enzyme and Microbial Technology41(2007)570–575571 adverse effect on juice color and represents a good substrate
for other enzymes.
The present study aims to evaluate?-d-glucosidase activity
in Tarocco orange and to determine the main physicochemical
and kinetic properties of such enzyme in order to underline its
role on the anthocyanins degradation during different ripening
stages.
2.Materials and methods
2.1.Plant materials
The study was performed on fruit from Tarocco cultivar(“Arcimusa”clone)
hand-harvested randomly from?ve trees,grafted on sour orange(C.aurantium
L.),and planted at the“Palazzelli”(Siracusa,Italy)experimental farm of the
CRA–Istituto Sperimentale per l’Agrumicoltura of Acireale(Catania,Italy).
Twenty fruit from each tree were collected at?ve different ripening stages,
from February to May,2005.Each fruit was squeezed separately using a
household juicer(Moulinex,Milan,Italy)and the cloudy juice obtained was
centrifuged at20,000×g for30min at5?C,in order to separate the residual
pulp from the juice.These fractions were stored singularly at?50?C prior to
physicochemical and enzymatic analysis.
2.2.Physicochemical analyses
Total soluble solid(TSS),total acidity(TA),ratio(TSS/TA)were determined
on cloudy juice according to standard methods[12].Ascorbic acid content was
determined on centrifuged juice by2,6-dichlorophenolindophenol titrimetric
method modi?ed by Rapisarda and Intelisano[13].Total anthocyanins in juice
(a)and extract(b)were determined spectrophotometrically by pH differential
method[14,15].For determination in juice(a)an aliquot of juice(2mL)was
diluted up to25mL with a pH1solution(125mL of0.2M KCl and375mL
of0.2M HCl).A second aliquot(2mL)was diluted up to25mL with a pH4.5
buffered solution(400mL of1M CH3CO2Na,240mL of1M HCl,and360mL
of H2O).Absorbance of the solutions was measured at510nm.Concentration
of anthocyanins was calculated by the equation:
C mg/L=(Abs pH1?Abs pH4.5)×484.82×1000 24,825×DF
where the term in parentheses is the difference of absorbance at510nm between pH1and pH4.5solutions,484.82is the molecular mass of cyanidin-3-glucoside chloride,24,825is its molar absorptivity(ε)at510nm in the pH1solution,and DF is the dilution factor.Accuracy of results by this method is supported by independent HPLC data.For anthocyanins extraction(b),3L of Tarocco orange juice previously centrifuged were loaded on a glass column(length40cm;i.d. 2cm)?lled with a nonpolar SDVB(styrene-divinylbenzene)resin Kastel S-112(Dow-Italia,Milano,Italy).After the adsorption,resin was washed with 2–3volumes of distillated water in order to obtain sugars and other soluble components elution.Anthocyanins were desorbed using1%HCl methanol(v/v) and different fraction were collected.Methanolic solution of the anthocyanins was concentrated by rotary evaporator maintaining the temperature below35?C. This extract was used for enzymatic assay.
The juice color was determined with a compact tristimulus chromameter (Minolta CR-300,Ramsey,NJ,USA)with an?8mm viewing aperture,white plate reference(Y=94.3;x=0.3142;y=0.3211)and C illuminant(CIE,2?observer)was used.Readings were expressed as L*,a*and b*parameters. Chroma[(a*2+b*2)1/2]and Hue angle[tan?1(b*/a*)]were calculated.
2.3.Enzymes determination
An aliquot of pulp(50g)was homogenised at4.0?C by adding200mL of extracting solution(citrate–phosphate buffer,0.1M;NaCl,1M;dithiothreitol, 1mM;pH5.0)[16].Suspension was maintained under stirring for2h at4.0?C, then centrifuged at10,000×g for15min at4?C.Starting from the extraction at optimum pH conditions,surfactants PEG400and PEG4000were tested by dissolving in1/3part of the extracting solution volume and adding to the suspension with the other2/3parts of the solution before pH correction.Tested concentrations of both surfactants were up to1.5%(w/v);besides,concentrations tested for PEG4000were2.3and4.0%(w/v).In order to maximize yield,the extract was:(a)saturated with ammonium sulphate80%,kept at4.0?C overnight and?ltrate under vacuum with a5892?lter(Whatman);(b)directly?ltrate and concentrated by tangential?ow ultra?ltration with50kDa cut-off membrane, and retentate utilised as enzymatic extract.The juice was directly analysed.
?G activity was determined by hydrolysis of synthetic(p-nitrophenyl-?-d-glucopyranoside,p NPG)and natural substrates(orange anthocyanins extract) at pH4.0and30?C[17].An aliquot of0.05mL of diluted enzyme was added to0.45mL of0.55×10?2M p NPG dissolved in0.1M citrate–phosphate(C–P) buffer pH5.0at25?C under continuous stirring.After1min,reaction was stopped by adding1mL sodium carbonate1M.Blank was carried out by invert-ing sodium carbonate with the enzyme solution.The absorbance of released 4-nitrophenolate ion was read at400nm and the concentration determined by usingε18,300M?1cm?1.One unit of enzyme activity was de?ned as the amount of enzyme releasing1?mol of4-nitrophenol min?1under assay conditions.
For anthocyanase determination[18]was used the cyanidin-3-glucoside extinction coef?cient(ε=24,825M?1cm?1)at510nm.Enzymatic units were de?ned as micromoles of anthocyanins.
Polyphenoloxidase(PPO,EC1.14.18.1)was assayed spectrophotometri-cally at505nm using3,4-dihydroxy phenylacetic acid(DOPAC)as phenolic substrate with MBTH(3-methyl-benzothyazolinone hydrazone)to trap the enzyme-generated ortoquinone[19,20].The absorbance was read at505nm and concentration determined by usingε25,400M?1cm?1.One unit of PPO activity was de?ned as the amount of enzyme which produces1?mol of adduct for min at25?C.
Protein concentration was determined after precipitation in7%(w/v) trichloroacetic acid by means of Coomassie Blue G250and by employing BSA as standard[21].The solvents and reagents not expressly speci?ed had a high degree of purity(RPE)and were supplied by Carlo Erba(Rodano,Italy).
2.4.Characterization ofβG
The following physicochemical and kinetic parameters were established: optimum temperature,optimum pH,inhibitions(glucose,fructose,ethanol), V max,K m,thermo-stability and molecular weight by SDS-PAGE.
2.4.1.Optimum temperature
The enzyme was assayed at temperatures from21to90?C(at pH5.0),with 600mL of1M sodium carbonate added in order to stop the reaction.
2.4.2.Optimum pH
Citric–citrate buffer solutions(0.1M)were prepared under different pH con-ditions(from2.5to8.0at30?C)in such a way as to assess the enzyme behaviour even in very different conditions to those of orange juices.
2.4.
3.Glucose and fructose inhibitions
Glucose and fructose inhibition tests were performed using sugar concen-trations not exceeding25g L?1(at pH5.0and30?C).The enzyme assay was carried out as previously described except as regards the sugar and buffer con-centrations,added in proportional amounts with respect to the?nal volume of the assay.
2.4.4.Kinetic parameters(V max and K m)
The behaviour of the enzyme(at pH5.0and30?C)was explained by the Michaelis–Menten equation and the kinetic parameters calculated by way of graphical extrapolation according to Lineweaver–Burk[22].Substrates were prepared increasing concentration until saturation.
2.4.5.Stability
Three aliquots of extract(60mL)were lyophilized and dissolved in10mL citric–citrate buffer0.1M pH5.0.Three tests were prepared by adding0.50?L to1.5mL of pasteurized(90?C for30min)and centrifuged orange juice;the three samples were put in thermostat at temperatures of37,52and70?C.
572R.N.Barbagallo et al./Enzyme and Microbial Technology 41(2007)570–575
2.4.6.SDS-PAGE (sodium dodecyl sulphate-polyacrylamide gel electrophoresis)
The enzyme extract was performed as described by Laemmhi [23].The samples,previously partially puri?ed by puri?ed by ammonium sulphate pre-cipitation (80%saturation)were put in touch with a 12%(w/v)polyacrylamide gel,both were dissolved according to the protein content determined by the above cited Coomassie Blue G250and by employing BSA as standard [21].
2.5.Statistical analysis
All determinations were conducted three times at least.Analysis of variance (ANOV A)of the data was evaluated by the Statistical Analysis System (SAS version 9.0).Duncan’s Multiple Range Test was employed to determine the statistical signi?cance of the differences between the means (p ≤0.05).
3.Results and discussion 3.1.Physicochemical analyses
Variations of physicochemical parameters during orange mat-uration process were reported in Table 1.Total soluble solids (TSS)showed a slight increase between February and ?rst days of May;after this period a decrease was noticed.Total acidity (TA)decreased quickly until 14March and then remained quite constant.The ratio (TSS/TA)values revealed that in March sam-ples reached the optimal maturity stage.Besides,although it was noticed an increasing of TSS and TA values at ?rst sampling of May,ratio value remained unchanged.Ascorbic acid content was stable during maturation except than in the last stage in which a decrease was observed.The anthocyanin content reached a max-imum in 14March when fruit were fully ripe.After this stage,values decreased.That was the most evident result between last two sampling,in which biochemical senescence process is more active.In samples withdrawn on 24May,anthocyanin content reduced to half in comparison with the maximum value.L *a *b *values described changes in juice color at different stages of Sicilian blood oranges.Apart from a slight loss in lightness (L *)and green-red (a *)values after 14March,juice did not show any other signi?cant variation of colour parameters,whereas the blue-yellow (b *)chromatism did not in?uence signi?cantly the organoleptic pro?le.Changes in total anthocyanin amount of blood orange juice did not seem to re?ect such visible changes in juice colour,since the maturation stages probably in?uenced stability of anthocyanins,as reported by other authors [24,25].3.2.Enzymes determination
The analysis of raw juice showed a ?G activity of 1.5×10?3U g ?1.Relatively to pulp,extraction tests at different pH conditions were performed (Fig.1).The maximum value of enzyme activity was noticed at pH 6.0,subsequently chosen for all extractions.A higher pH cause an increasing of dissociation rate of pulp pectins carboxylic groups;it causes an increasing of the intra and inter-molecular electrostatic repulsions between the pectin chains and,probably,even between enzyme and pectin,resulting in an easier ?G release in extraction solutions.On residual part of the ?rst extraction,constituted by pulp and a gelatinous layer (calcium pectate),a second extraction was car-
T a b l e 1P h y s i c o -c h e m i c a l c h a r a c t e r i s t i c s o f b l o o d o r a n g e j u i c e h a r v e s t e d a t ?v e d i f f e r e n t r i p e n i n g s t a g e s
p H
T S S (%)
T A (%)
T S S /T A
A s c o r b i c a c i d (m g %)A n t h o c y a n i n s (m g /L )L *
a *
b *
8F e b r u a r y 3.44±0.02a 11.61±0.2a 1.35±0.1a 8.60±0.7a 66.48±1.4b 89.70±11.35a 37.37±3.72a 23.89±0.58a 41.68±1.40a 14M a r c h 3.46±0.05a 11.98±0.5a 1.02±0.2a 11.75±1.6b 66.93±1.8b 156.00±12.90c 38.05±2.19a 24.76±0.19a 40.86±0.91a 11A p r i l 3.48±0.04a 12.00±0.5a 1.09±0.1a 11.01±0.8a b 65.24±0.9b 114.56±10.29b 35.31±1.03b 29.36±0.28b 37.18±2.33a 4M a y 3.48±0.02a 12.35±0.4a 1.19±0.2a 10.38±1.3a b 68.09±2.8b 79.63±7.15a 31.31±1.03b 31.36±0.28b 36.18±2.63a 24M a y 3.41±0.05a 11.13±0.5a 1.09±0.1a 10.21±0.8a b 48.46±6.7a 75.01±6.95a 29.31±1.03b
31.30±0.26b 36.10±
2.35a N o t e :M e a n o f s e p a r a t e 20f r u i t j u i c e s d e t e r m i n a t i o n .M e a n s i n a s a m e c o l u m n f o l l o w e d b y t h e s a m e l e t t e r a r e n o t s i g n i ?c a n t l y d i f f e r e n t a t t h e p ≤0.05l e v e l a c c o r d i n g t o D u n c a n ’s m u l t i p l e r a n g e t e s t .
R.N.Barbagallo et al./Enzyme and Microbial Technology 41(2007)570–575
573
Fig.1.Effect of pH extraction on ?G activity.
ried out,that led to a limited activity recover (lower than 5%).Total pulp activity resulted 8–10times higher,for all samples,than the centrifuged juice activity,since the ?G is mostly bond to the solid fraction of fruit and,presumably,to pectin chains.In order to increase the ?G extraction,it was tried to add a non ionic surfactant,polyethylene glycol (PEG)at two different molecu-lar weights (400and 4000),as suggested by Gunata [16]for ?G extraction from grapes skin.
The results showed a worsening in extraction yield with rela-tive speci?c activity of ?G extracted of 79.74and 64.26%,with PEG 400and 4000surfactants,respectively.Probably,the dif-ferent behaviour depends to the presence of a wax layer over the grapes and/or to different molecular structure of the enzyme.The use of ammonium sulphate precipitation (80%saturation)reduced the activity to less than 1/3,so ultra?ltration was pre-ferred since its higher yield (>80%).
Fig.2reports anthocyanins and ?G changes in fruit,from February to May 2005.Anthocyanin concentrations in fruit reached a maximum at day 34and then decreased,while ?G showed an opposite trend,proportionally increasing its activity,with a 80%correlation coef?cient (95%con?dence interval).Then,it would seem that ?G plays a role in anthocyanins degra-dation of Tarocco fruit at the end of ripening.In fact,loss of glucosidic substituent from anthocyanins by ?G hydrolisis destabilizes the anthocyanins leading to adverse effects on color quality,as the aglycon is extremely unstable.The anthocyanidins may be a good substrate for oxidases such as polyphenoloxidase (PPO)in a successive enzymatic degradation process [26].PPO activity was found in Tarocco orange (with a range from
Febru-
Fig.2.Anthocyanins content and ?-glucosidase activity during fruit
ripening.
Fig.3.Enzyme kinetics with synthetic substrate (p NPG,3a)and natural sub-strate (anthocyanins,3b).
ary to May of 2.50–2.99×10?4Ug ?1),although with lower value than ?G (ca.1/30).Presence of the PPO activity in blood orange indicates that this enzyme could play a role on antho-cyanidin degradation.3.3.Characterization of βG
The enzyme involved in p NPG hydrolysis followed a Michaelis–Menten kinetics (Fig.3a),with K m 2.67×10?4M and V max di 2.1×10?2nmol/mg proteins min.With regard to the hydrolysis of anthocyanins obtained from Tarocco extract (Fig.3b),it was observed a six times reduc-tion of enzymatic activity and enzyme inhibition at high anthocyanins concentration (product inhibition).The enzyme behaviour on anthocyanins substrate cannot be explained by Michaelis–Menten equation.Referring to the point of maximum,apparent K m was 2.1×10?1M and V max was 3.3×10?3nmol/mg proteins min.Therefore,?G speci?city on synthetic substrate compared to anthocyanins,calculated from V max /K m ratios of respective substrates,resulted 400times higher.
Relative activity reached maximum value at pH 4.5(Fig.4),with a 35%of relative activity at physiological pH of the fruit (3.5).This course resulted similar in ?G from microbial sources,as Aspergillus niger [27,28].Therefore,it could be supposed that the reaction mechanism is always an acid–base reaction with involvement of at least two carboxylic groups [28].Optimum temperature (Fig.5)resulted quite high for a vegetable source
574R.N.Barbagallo et al./Enzyme and Microbial Technology 41(2007)
570–575
Fig.4.Effect of pH on ?-glucosidase relative
activity.
Fig.5.Effect of temperature on ?-glucosidase relative activity.
enzyme (60?C)and even in this case similar to enzyme from microbial source [29].
The enzyme was not inhibited by fructose and ethanol,while glucose inhibition was noticed.Kinetic study
by
Fig.6.Glucose inhibition according to Lineweaver–Burk (a);thermal stability of ?-glucosidase
(b).
Fig.7.Arrhenius plot for heat inactivation of ?-glucosidase.
Lineaweaver–Burk interpolation,allowed to establish that the inhibition was competitive,with an inhibition constant value K i ,equal to 3.08×10?2M (Fig.6a).?G stability tests allowed to determine,by activity versus time plot (Fig.6b),the enzyme inactivation constants (k in )at various temperatures.By these results,an inactivation energy of 30kcal/mol K was calculated by the Arrhenius plot (Fig.7).Such results,expressed as second Bigelow law (ln D1/D2= T /z ),allowed to determine for ?G a decimal reduction time (D )of about 3min at 75?C and a deci-mal reduction temperature (z )of about 9.5?C.Then,the enzyme showed a good stability so it could play a role in thermal process of blood orange juice.
SDS-polyacrylamide gel electrophoresis of enzyme partially puri?ed by ammonium sulphate precipitation (80%saturation)was performed as shown in Fig.8.There are two major bands corresponding to the molecular weight of 65and 55kDa.
In conclusion,results obtained put in evidence for the ?rst time presence of ?G in blood orange cv.Tarocco .The enzyme activity in pulp resulted higher than in centrifuged juice,showing that ?G is mainly bond to the solid part of fruit and probably to pectin chains.Speci?city resulted higher for synthetic
substrate
Fig.8.SDS-polyacrylamide gel electrophoresis of pulp and partially puri?ed ?https://www.doczj.com/doc/48473763.html,ne 1:10?L of protein molecular weight standard;Lane 2:10?L of crude enzyme;Lane 3:10?L of enzyme extract.
R.N.Barbagallo et al./Enzyme and Microbial Technology41(2007)570–575575
than for natural substrate,with a different kinetic behaviour.The enzyme followed Michaelis–Menten kinetics and showed some properties(optimal pH and temperature conditions,glucose competitive inhibition)similar to those found for?-glucosidase from A.niger[30].Finally,relatively to fruit,it was reported a relation between?G activity increasing and anthocyanins level decreasing,so it is possible to hypotize the enzyme is involved in anthocyanins degradation reactions during?nal ripening stage.
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可数名词与不可数名词 名词分可数名词与不可数名词。 1．有些名词总是用作可数名词的，如： leg，dog，pen．有些名词总是用作不可数名词，如： pork，gold，honesty．有些则有时用作可数名词，有时用作不可数名词，如：It is made of glass.（不可数） He held a glass.（可数） 与5类名词的关系 区分5类名词对决定一个名词是可数还是不可数有极其重要的意义。C代表可数（Countable），用U代表不可数（Uncountable）。1．大多数普通名词为可数名词，如： a chair，another car，dogs． 2．多数集体名词也是可数名词，如：（a）family，（each）class，（all） parties，（different） nations。 3．专有名词，多数作不可数名词，如：London，China，Ham-bet，Neptune；但有些为可数名词，如 Communists，English-men。4．物质名词一般不可数，如：milk，gold，coffee，beer．但有些可用作可数名词，表示特殊意义，如：an ice-cream（一份冰淇淋），a light rain（一阵小雨）。 5．多数的抽象名词既可作不可数名词，也可作可数名词（这时意思有些变化），如： 不可数可数beauty 美 a beauty 美人 disappointment 失望 a disappointment 失望的事 C．普通名词和物质名词 不过一个名词的可数与不可数问题最终还是靠习惯决定，习惯用法是自然形成的，不能靠简单的条文来推断。虽说表示可数的东西为可数名词，否则为不可数名词，但总有些特殊情况。在表示定形之物时，物质名词也可用作可数名词，在强调某种特性时，普通名词也可变成不可数名词。 1．气体名称通常作不可数名词，如：oxygen（氧气），hydrogen（氢气）。但odour（气味），flavor（味道），cloud（云）是可数名词；而fire则既可作不可数名词，也可作可数名词。 2．液体名称一般为不可数名词，如：milk，water；但beverage（饮料），cocktail（鸡尾酒）为可数名词，而juice（汁）、sauce （调味液）、liquor（酒）既可作可数名词，也可作不可数名词。 3．药品名称通常不可数，如： codeine；但antibiotic（抗生素），insecticide（杀虫剂），vitamin（维生素）都是可数的。4．植物中有些的名称既作可数名词，也可作不可数名词，如： 可数不可数 a pine 松树 pine 松木 a pepper 青椒 pepper 胡椒粉 5．表示天气的名词多作不可数名词，如：lightning（闪电），thunder（雷），snow，但有些为可数名词，如： comet（慧星），sunbean（阳光），ray（光线）。有些可用作两类，如： mist（浓雾），dew（露水），rain。 6．表示动物的名词一般为可数名词，如： monkey，elephant，shrimp（虾），但有些可用于两类情况，如： 可数不可数 a chicken鸡 chicken鸡肉 a duck 鸭 duck鸭肉 a fish鱼 fish 鱼（肉） 7．物质名词一般不可数，如： iron，plaster（石膏），mercury（水银）。有些两者都可以，如：chalk（粉笔），brick（砖），coal（煤）。 D．集体名词 26 有个别集体名词可用作不可数名词，如： police（警察总称），cattle（牲口），produce（农产品），vegetation（植物），clothing（衣服），furniture（家具），pottery（陶器）。 E．抽象名词 27 1．在一万个抽象名词中约有 72％（约7 200字）常常或有时既作不可数名词，又作可数名词，如： belief，beliefs； birth，births； hope，hopes；fear，fears。
如何写先进个人事迹 篇一：如何写先进事迹材料 如何写先进事迹材料 一般有两种情况：一是先进个人，如先进工作者、优秀党员、劳动模范等；一是先进集体或先进单位，如先进党支部、先进车间或科室，抗洪抢险先进集体等。无论是先进个人还是先进集体，他们的先进事迹，内容各不相同，因此要整理材料，不可能固定一个模式。一般来说，可大体从以下方面进行整理。 (1)要拟定恰当的标题。先进事迹材料的标题，有两部分内容必不可少，一是要写明先进个人姓名和先进集体的名称，使人一眼便看出是哪个人或哪个集体、哪个单位的先进事迹。二是要概括标明先进事迹的主要内容或材料的用途。例如《王鬃同志端正党风的先进事迹》、《关于评选张鬃同志为全国新长征突击手的材料》、《关于评选鬃处党支部为省直机关先进党支部的材料》等。 (2)正文。正文的开头，要写明先进个人的简要情况，包括：姓名、性别、年龄、工作单位、职务、是否党团员等。此外，还要写明有关单位准备授予他(她)什么荣誉称号，或给予哪种形式的奖励。对先进集体、先进单位，要根据其先进事迹的主要内容，寥寥数语即应写明，不须用更多的文字。 然后，要写先进人物或先进集体的主要事迹。这部分内容是全篇材料
的主体，要下功夫写好，关键是要写得既具体，又不繁琐；既概括，又不抽象；既生动形象，又很实在。总之，就是要写得很有说服力，让人一看便可得出够得上先进的结论。比如，写一位端正党风先进人物的事迹材料，就应当着重写这位同志在发扬党的优良传统和作风方面都有哪些突出的先进事迹，在同不正之风作斗争中有哪些突出的表现。又如，写一位搞改革的先进人物的事迹材料，就应当着力写这位同志是从哪些方面进行改革的，已经取得了哪些突出的成果，特别是改革前后的．经济效益或社会效益都有了哪些明显的变化。在写这些先进事迹时，无论是先进个人还是先进集体的，都应选取那些具有代表性的具体事实来说明。必要时还可运用一些数字，以增强先进事迹材料的说服力。 为了使先进事迹的内容眉目清晰、更加条理化，在文字表述上还可分成若干自然段来写，特别是对那些涉及较多方面的先进事迹材料，采取这种写法尤为必要。如果将各方面内容材料都混在一起，是不易写明的。在分段写时，最好在每段之前根据内容标出小标题，或以明确的观点加以概括，使标题或观点与内容浑然一体。 最后，是先进事迹材料的署名。一般说，整理先进个人和先进集体的材料，都是以本级组织或上级组织的名义；是代表组织意见的。因此，材料整理完后，应经有关领导同志审定，以相应一级组织正式署名上报。这类材料不宜以个人名义署名。 写作典型经验材料-般包括以下几部分： (1)标题。有多种写法，通常是把典型经验高度集中地概括出来，一
【英语词汇】 property、character、characteristic、 trait、attribute、feature 佳中 这组词常用于表示人或物的特征。 property 多指物的物理或化学特性，或同类事物所共有的特性，一般不用于指人。 1）The two elementary forms of carbon have very different properties. 碳的这两个基本形式的性质大不相同。 2）We may not be able to identify a substance from a single property. 凭单一特性我们也许不能别出一种物质。 character泛指人的性格特征，或指人的独特的典型的特征。 1) Indeed, he is a very kind man at heart. What you know about him is not his real character. 确实他是一个非常心地善良的人。你对他的了解并不是他的真正品格。 2）A man’s character can be measured by the types of men with whom he associates. 一个人的性格可从他交往何种类型的人加以判断。 characteristic可指人或事物所具有的、不同于其他人或物的个性或性质。指人时是character 中的具体特征或特点。 1）She united with herself the characteristics of two distinct persons. 她身上具有两个截然不同的人的特点。 2）Reaction to strong stimuli from the outside world is a characteristic of all animals. 对外界的刺激产生反应是所有动物的一个特性。 3) This town has all the characteristics of a typical seaside resort. 这个小城镇具有所有典型的的海滨特色。 trait 与character一样，指人的具体性格的特征, 侧重于指先天行为模式或性格特征。 1）Enthusiasm and honesty are the chief traits / characteristics of his character. 热情和诚实是的他的性格的两个主要特征。 2) The world discriminates one on the basis of clearly genetic traits, such as physical beauty and musical talent. 世界常根据显著遗传特点区分人，如长相美和音乐天赋等。
不可数名词和可数名词 不能按照个数计算的普通名词叫不可数名词；如：juice, milk, water, beef, chicken 等。 能按照个数计算的普通名词叫可数名词。可数名词有单复数两种形式。指一个人或一件事用单数形式a/an ；指两个人及多个人或事物时用复数形式。可数名词由单数形式变为复数形式的规则如下： ①一般情况，加-s。 女口：books, dogs, days, trees 等。 ②单词以s, x, ch, sh 结尾的，加-es。 女口：classes, watches ,boxes, brushes 等。 ③单词以“辅音字母+y”结尾，将y变i，加-es。 女口：stories, cities, families, babies 等。 ④以o结尾有生命的名词加-es ;无生命的名词加-s。 女口：有生命：heroes, potatoes, tomatoes, man goes 等。 无生命：photos, pia nos, radios, zoos 等。 ⑤一些以f或fe结尾的单词，把f、fe变成ve加-s。 女口：life-lives, knife-knives 等。 ⑥不规则变化。 女口：man-men, woman-women, child-children, foot-feet, tooth-teeth 等。 ⑦单复数同形。 女口：deer, sheep, fish, Chinese, Japanese 等。 一、根据句意填空。 1. Look at those ______ ild) 2.1 can see a ___________ ding n ear the door. (policema n) 3. Do you want some ________ f or dinner? (potato) 4. In autu mn, you can see a lot of ______ ound. (leaf) 5. He has two ______ ne is blue, the other is yellow. (box) 6. Two ________ live in this build ing. ( family )
小学生个人读书事迹简介怎么写800字 书,是人类进步的阶梯,苏联作家高尔基的一句话道出了书的重要。书可谓是众多名人的“宠儿”。历来,名人说出关于书的名言数不胜数。今天小编在这给大家整理了小学生个人读书事迹,接下来随着小编一起来看看吧! 小学生个人读书事迹1 “万般皆下品,惟有读书高”、“书中自有颜如玉,书中自有黄金屋”,古往今来,读书的好处为人们所重视,有人“学而优则仕”,有人“满腹经纶”走上“传道授业解惑也”的道路……但是,从长远的角度看,笔者认为读书的好处在于增加了我们做事的成功率,改善了生活的质量。 三国时期的大将吕蒙,行伍出身,不重视文化的学习,行文时,常常要他人捉刀。经过主君孙权的劝导,吕蒙懂得了读书的重要性,从此手不释卷,成为了一代儒将,连东吴的智囊鲁肃都对他“刮目相待”。后来的事实证明,荆州之战的胜利,擒获“武圣”关羽,离不开吕蒙的“运筹帷幄,决胜千里”,而他的韬略离不开平时的读书。由此可见,一个人行事的成功率高低,与他的对读书,对知识的重视程度是密切相关的。 的物理学家牛顿曾近说过,“如果我比别人看得更远,那是因为我站在巨人的肩上”,鲜花和掌声面前,一代伟人没有迷失方向,自始至终对读书保持着热枕。牛顿的话语告诉我们,渊博的知识能让我们站在更高、更理性的角度来看问题,从而少犯错误,少走弯路。
读书的好处是显而易见的,但是,在社会发展日新月异的今天,依然不乏对读书,对知识缺乏认知的人,《今日说法》中我们反复看到农民工没有和用人单位签订劳动合同,最终讨薪无果;屠户不知道往牛肉里掺“巴西疯牛肉”是犯法的;某父母坚持“棍棒底下出孝子”,结果伤害了孩子的身心,也将自己送进了班房……对书本,对知识的零解读让他们付出了惨痛的代价,当他们奔波在讨薪的路上,当他们面对高墙电网时,幸福,从何谈起?高质量的生活,从何谈起? 读书,让我们体会到“锄禾日当午,汗滴禾下土”的艰辛;读书,让我们感知到“四海无闲田,农夫犹饿死”的无奈;读书,让我们感悟到“为报倾城随太守,西北望射天狼”的豪情壮志。 读书的好处在于提高了生活的质量,它填补了我们人生中的空白,让我们不至于在大好的年华里无所事事,从书本中,我们学会提炼出有用的信息,汲取成长所需的营养。所以,我们要认真读书,充分认识到读书对改善生活的重要意义,只有这样,才是一种负责任的生活态度。 小学生个人读书事迹2 所谓读一本好书就是交一个良师益友,但我认为读一本好书就是一次大冒险,大探究。一次体会书的过程,真的很有意思,咯咯的笑声,总是从书香里散发;沉思的目光也总是从书本里透露。是书给了我启示,是书填补了我无聊的夜空,也是书带我遨游整个古今中外。所以人活着就不能没有书,只要爱书你就是一个爱生活的人,只要爱书你就是一个大写的人,只要爱书你就是一个懂得珍惜与否的人。可真所谓
英语中可数名词与不可数名词的区别 西永安小学王爱芳 在英语中很多名词既可以用作可数,也可以作不可数,判断其可数与不可数时,依据就是其意思的变化.不可能有名词在作同一词义时既可数又不可数的情况. (1)表示动物的一些词一般可数,但指肉时是不可数． 如:fish, chicken, lamb 等． (2)物质名词不可数,如rubber, glass, iron． 用作可数名词时词义有变化,如 a rubber(一块橡皮擦), a glass (一个玻璃杯), a pair of glasses (一副眼镜)an iron(一个慰斗)． (3)抽象名词显然不可数,但指具体的意义时又是可数,如: success(成功,不可数) ——a success( 一件成功的事,可数) experience (经验,不可数) —experiences (经历,可数) in surprise 中surprise 指一种情感，是抽象名词不可数．It’s a surprise．．．中surprise 是指一件事情,是具体名词可数． 即：有些词通常既可数又不可数，最简单的判断方法是：判断其所指的是“具体的”还是“抽象的”。举例子： Lactose, A (a) sugar B(present) in milk, is one C(of simple sugars) used in D(food) preparations for infants. 前面的sugar是指“牛奶”中的糖分（物质的一种属性），此时为不可数名词，在句中作同位语，不需要仍何冠词。如：Lactose is sugar，not salt. present 为形容词作定语。one of 指特定群体中的一部分，必须接定冠词，此时sugar为可数名词指不同形式的糖类。food就是不数名词。 例如：Experience 是可数名词时是经历 不可数名词时是经验 experience n. 1. 经验,体验[U][(+of/in)] She had no experience of life at all. 她毫无生活经验。 Have you had any experience of teaching English? 你有过教英语的经验吗? 2. 经历,阅历[C] Please tell us about your experiences in Africa. 请跟我们谈谈你在非洲的经历。 I had a rather odd experience the other day. 前些天我有过一次相当奇怪的经历。 vt. 1. 经历;体验 The city experienced over 2,000 such incidents last year. 去年这座城市发生过二千次以上这类事件。 2. 感受;遭受
Characteristics of science Charles Van Doren 1.Science, in our common everyday sense of the word, is a human activity characterized by three things. 2.First, science is practiced by special people with a specific view of the world. Scientists try to be objective, unsentimental and unemotional. They do not let their feelings get in the way of their observations of real things, facts, as they call them. They often work in laboratories or in other areas where they can carefully control what they are working on. They do not just wander out onto the dock at sunset and look at the world with wonder, as a poet might. Ideally, they are also both honest and check them out and then utilize them in their findings so others can check them out and then utilize them in their own work. They do not claim more than they can prove, and often even less. But they are very proud of their calling and prefer to talk to other scientists rather than anybody else, especially poets, who tend to make them feel uncomfortable, to put them down.(Of course poets also feel scientists return the favor.) 3.Second, science deals almost exclusively with things, not ideas or feelings, and with the external world and its workings, not inner states and their workings, despite the effort of some psychologists to be or seem scientific. The human body is considered to be or seem scientific. The human body is considered to be a part of the external world; the soul is not. Therefore, scientists work to understand the body but not the soul. Most scientists doubt the soul exists. The solar system and the universe are also part of the external world, although we have little enough direct evidence of their mode of existence. Scientists tend to assume the basic conditions of nature on Earth are the same everywhere in the cosmos. 4.Mankind is only questionably part of the external world in this sense. Scientists are generally reluctant to deal with the behavior of large groups of men and women. Thus economists, for example, struggle to be considered scientists, but usually in vain. The external world of scientists contains some things, like quanta, quarks and quasars, that are as mysterious as angels and normally as invisible. But this does not trouble them, as they believe they can deal effectively with the elementary particles that they cannot see and according to the uncertainty principle never can see, but not with angels, which will probably never appear to scientists because scientists do not believe in them. 5.When you come right down to it, the external world is anything that scientists can measure and describe in mathematical terms, and it excludes everything they cannot. This means the external world is a rather hazy notion, but the idea behind it is not hazy at all. 6.Third, science deals with whatever it deals with in a special way, employing special methods and a language for reporting results that is unique to it. The best-known method, but not necessarily the most often employed, consists of experiment, Which involves getting an idea – from where, most scientists do not question – framing it in a testable hypothesis, and then testing the hypothesis in a
如何区分可数与不可数名词 具体名词可数，抽象名词不可数。 具体名词: 看得见的某种人、某样东西、某个地方的名称，你可以把它拆分成很多独立而分离的个体去看待。 an offender，most offenders；an English learner，English learners；one product，different products；his computer，their computers； a museum，virtual museums；this area，those areas 抽象名词: 看不见摸不着, 只可意会不可言传，只存在你脑里的概念，需要你用心去感受的，不是一个有形的物体。 advice，anger，assistance，courage，damage，evidence，happiness，harm，health，hospitality，information，knowledge，luck，music，patience，progress，permission，safety，traffic，travel，violence，wealth，work 但抽象不可数名词中有些虽然不是可拆分的个体，有时候却需要去量化它，那么可以通过数“单位词”来显示这些名词的数量。如： a piece of advice，a piece of evidence，a stroke of luck，a form of travel，an act of violence 有些具体名词，虽然真真实实看到了它是存在的物体，却是不可数名词，因为把它们看做了一个整体的类别。如： (an item of)baggage，(a loaf of)bread，cash，coffee，coal， (a piece of )furniture，garbage，(a slice of)meat， scenery， (a dish of)spaghetti (具体不可数名词，如果不看做一个种类，而是要指一部分，去量化这些物品，也是可以用量词来表示数量的。) 有些抽象名词，虽然也是透明不可见的，却也是可数的。因为它们虽是无形的存在，但却可以有具体的分类和特征。如 skill（s）,industry（-ies）,system（s）,factor（s）,government（s），situation（s），j ob（s），rate（s），brand（s）,salary（-ies）. 双性名词 experience 1.They want someone with experience for this job. 统称“经验”这种个人能力/履历，是一个人的内在—>不可数
个人先进事迹简介 01 在思想政治方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.利用课余时间和党课机会认真学习政治理论,积极向党组织靠拢. 在学习上,xxxx同学认为只有把学习成绩确实提高才能为将来的实践打下扎实的基础,成为社会有用人才.学习努力、成绩优良. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意识和良好的心理素质和从容、坦诚、乐观、快乐的生活态度,乐于帮助身边的同学,受到师生的好评. 02 xxx同学认真学习政治理论,积极上进,在校期间获得原院级三好生,和校级三好生,优秀团员称号,并获得三等奖学金. 在学习上遇到不理解的地方也常常向老师请教,还勇于向老师提出质疑.在完成自己学业的同时,能主动帮助其他同学解决学习上的难题,和其他同学共同探讨,共同进步. 在社会实践方面,xxxx同学参与了中国儿童文学精品“悦”读书系,插画绘制工作,xxxx同学在班中担任宣传委员,工作积极主动,认真负责,有较强的组织能力.能够在老师、班主任的指导下独立完成学院、班级布置的各项工作. 03 xxx同学在政治思想方面积极进取,严格要求自己.在学习方面刻苦努力,不断钻研,学习成绩优异,连续两年荣获国家励志奖学金；作
为一名学生干部,她总是充满激情的迎接并完成各项工作,荣获优秀团干部称号.在社会实践和志愿者活动中起到模范带头作用. 04 xxxx同学在思想方面,积极要求进步,为人诚实,尊敬师长.严格 要求自己.在大一期间就积极参加了党课初、高级班的学习,拥护中国共产党的领导,并积极向党组织靠拢. 在工作上,作为班中的学习委员,对待工作兢兢业业、尽职尽责 的完成班集体的各项工作任务.并在班级和系里能够起骨干带头作用.热心为同学服务,工作责任心强. 在学习上,学习目的明确、态度端正、刻苦努力,连续两学年在 班级的综合测评排名中获得第1.并荣获院级二等奖学金、三好生、优秀班干部、优秀团员等奖项. 在社会实践方面,积极参加学校和班级组织的各项政治活动,并 在志愿者活动中起到模范带头作用.积极锻炼身体.能够处理好学习与工作的关系,乐于助人,团结班中每一位同学,谦虚好学,受到师生的好评. 05 在思想方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.作为一名共产党员时刻起到积极的带头作用,利用课余时间和党课机会认真学习政治理论. 在工作上,作为班中的团支部书记,xxxx同学积极策划组织各类 团活动,具有良好的组织能力. 在学习上,xxxx同学学习努力、成绩优良、并热心帮助在学习上有困难的同学,连续两年获得二等奖学金. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意 识和良好的心理素质.
character, characteristic, trait, personality, feature, attribute, property 一、character n. 性格，品质，人物，角色；[计]字符；指个人、社会、民 族等的“特性，性格”，或指人的独特的典型的特征或性格。通常是自身素质的体现，强调后天培养的结果。例如： （1）All the characters in this book are imaginary. 这本书中的人物都是虚构的。（2）Dr. Watson is a character in the Sherlock Holmes stories. 华生医生是福尔摩斯探案故事中的一个人物。 （3）What's your most special characters? 你个性上最大的特点是什么？ （4）That man has a firm character now, but in his youth, his charater was weak. 那个人现在性格坚强，但是在少年时代，他性格软弱。 （5）Indeed, he is a very kind man at heart. What you know about him is not his real character. 确实他是一个非常心地善良的人。你对他的了解并不是他的真正品格。 （6）A man’s character can be measured by the types of men with whom he associates. 一个人的性格可从他交往何种类型的人加以判断。 （7）He seems to be a man of good character. 看来他是一个品格优良的人。（8）I'd like to use small characters of this essay. 这个作文我想用小号字符。 二、characteristic 指“特征，特点，规格参数表”，指某人或某物恒定 的、先天有别于他人或他物的内部或外部属性和特征，并非性格。可指人或事物所具有的、不同于其他人或物的个性或性质。指人时是character（性格）中的具体特征或特点。例如： （1）What characteristics distinguish the Chinese from the Japanese? 中国人不同与日本人的特征是什么？ （2）She united with herself the characteristics of two distinct persons. 她身上具有两个截然不同的人的特点。 （3）She has Asiatic characteristics. 她具有亚洲人的特点。 （4）Reaction to strong stimuli from the outside world is a characteristic of all animals. 对外界的刺激产生反应是所有动物的一个特性。
优秀党务工作者事迹简介范文 优秀党务工作者事迹简介范文 ***，男，198*年**月出生，200*年加入党组织，现为***支部书记。从事党务工作以来，兢兢业业、恪尽职守、辛勤工作，出色地完成了各项任务，在思想上、政治上同党中央保持高度一致，在业务上不断进取，团结同事，在工作岗位上取得了一定成绩。 一、严于律己，勤于学习 作为一名党务工作者，平时十分注重知识的更新，不断加强党的理论知识的学习，坚持把学习摆在重要位置，学习领会和及时掌握党和国家的路线、方针、政策，特别是党的十九大精神，注重政治理论水平的提高，具有坚定的理论信念;坚持党的基本路线，坚决执行党的各项方针政策，自觉履行党员义务，正确行使党员权利。平时注重加强业务和管理知识的学习，并运用到工作中去，不断提升自身工作能力，具有开拓创新精神，在思想上、政治上和行动上时刻同党中央保持高度一致。 二、求真务实，开拓进取 在工作中任劳任怨，踏实肯干，坚持原则，认真做好学院的党务工作，按照党章的要求，严格发展党员的每一个步骤，认真细致的对待每一份材料。配合党总支书记做好学院的党建工作，完善党总支建设方面的文件、材料和工作制度、管理制度等。
三、生活朴素，乐于助人 平时重视与同事间的关系，主动与同事打成一片，善于发现他人的难处，及时妥善地给予帮助。在其它同志遇到困难时，积极主动伸出援助之手，尽自己最大努力帮助有需要的人。养成了批评与自我批评的优良作风，时常反省自己的工作，学习和生活。不但能够真诚的指出同事的缺点，也能够正确的对待他人的批评和意见。面对误解，总是一笑而过，不会因为误解和批评而耿耿于怀，而是诚恳的接受，从而不断的提高自己。在生活上勤俭节朴，不铺张浪费。 身为一名老党员，我感到责任重大，应该做出表率，挤出更多的时间来投入到**党总支的工作中，不找借口，不讲条件，不畏困难，将总支建设摆在更重要的位置，解开工作中的思想疙瘩，为攻坚克难铺平道路，以支部为纽带，像战友一样团结，像家庭一样维系，像亲人一样关怀，践行入党誓言。把握机遇，迎接挑战，不负初心。
Communication skill is the most important characteristic of successful leadership A successful leadership can never fail to attract people’s eyes with some special characteristics. Communication skill has been considered the key to success to leadership. From my personal perspective, whether it is the most important characteristic depends on what kind of leadership to talk about. For business leadership, it is no exaggeration to say that communication is the crucial quality, since it can attract more clients and customers. A good leadership of a big company always consults his or her employees before making a decision for the company. For example, a famous entrepreneur in my hometown decided to open a supermarket in my hometown many years ago during the financial crises. The employees and the residents in our hometown had no doubt that the supermarket would be a success. Because the leader of that company is gregarious, he appeased his stuffs when they lose confidences and talk with other people to let them believe in him to get their support. His good communication skills help him gain a good reputation both from employees and customers. This example validated my assumption that communication is extremely vital to the business leaders. However, communication skills can be less necessary for political
可数名词与不可数名词的区别 普通名词所表示的人或事物是可以按个数计算的，这类名词叫可数名词。可数名词分为个体名词(表示某类人或事物中的个体，如worker, farmer, desk, factory等)和集体名词(表示作为一个整体来看的一群人或一些事物，如people, family 等)。如果普通名词所表示的事物是不能按个数来计算的，这类名词就叫不可数名词。不可数名词分为物质名词(表示无法分为个体的物质，如meat, rice, water, milk, orange 等)和抽象名词(表示动作、状态、情况、品质等抽象概念，如work, homework, time, health, friendship等)。 二、关于可数名词 名词可分为可数名词和不可数名词两部分。其中，可数名词是表示能够计算的人或物的名称，他们通常有单数和复数的形式。 单数通常用a,an或者是one来表示。an用在元音字母的前面。如：a desk, an apple, one boy. 1、直接在单词的后面加-s. photo---photos book---books egg---eggs student---students pen---pens village---villages building---buildings cloud---clouds flower---flowers hand---hands map---maps girl---girls 2、如果单词以s,x,ch,sh结尾，通常要在单词后面加-es. bus---buses class---classes box---box dress---dresses peach---peaches watch---watches fish---fishes 3、以辅音字母+y结尾的单数名词要把y变为i，再加-es.如果y的前面是元音字母，则直接加上-s. family---families story---stories baby---babies day---days toy---toys boy---boys 4、以f,fe结尾的单词，要把f,fe变为v，再加-es. knife---knives wolf---wolves shelf---shelves 5、以o结尾的单词一般加-s构成复数，但potato, tomato,hero等词要加-es构成复数。 radio---radios photo---photos piano---pianos zoo---zoos studio---studios potato---potatoes tomato---tomatoes hero---heroes 6、一些特殊的不规则名词的复数。 goose---geese foot---feet tooth---teeth woman---women man---men sheep---sheep fish---fish deer---deer people---people child---children ox---oxen mouse---mice 7、be和指示代词的复数。 is---are am---are this---these that---those it---they 8、有些名词是通常以复数形式出现的，如：shoes, pants, boots, glasses等。三、关于不可数名词 1. 不可数名词没有复数，当它作句子的主语时，谓语动词要用单数形式。 如：The food is very fresh. 食品很新鲜。 2. 有的不可数名词也可以作可数名词，有复数形式，但他们的意义往往发生变化。 如：water (水) → waters (水域) orange (橘汁) → oranges (橘子) 3. 很多的不可数名词表示泛指时为不可数，表示种类时就可数，但意义大多不发生变化。 如：fruit → fruits food → foods fish → fishes hair → hairs 一、不可数名词的概念 1. 一般来说，不可数名词主要是以物质名词与抽象名词为主。它们通常没有复数形式，也不能与a ,an 连用。在表示“一”或“几”的数量概念时，不可数名词必须与相应的量词连用。如果时表示复数的数量关系时，则把量词变化，不可数名词不变。修饰不可数名词的数量词语有：some, any, much, a lot of, a little等。