分类法
分类就是按照事物的不同特点将它们划成多个类别。事物可以按照不同的标准进行分类，标准则取决于分类的成因。例如，在分析某系学生的构成情况时，如果想了解他们的学习情况，可以将他们根据考试成绩划分为若干组；如果想研究是否有可能组织一场足球比赛或是篮球比赛，可以根据对足球和篮球的爱好程度把学生划分成若干组。
不管分类的目的是什么，分类的标准必须具有普适性和排他性，也就是说分类标准必须覆盖分类样本集中的所有样本元素，而且样本集中的任一元素只能隶属于分类标准项次中的唯一一项。例如，把学生分成男生、女生和运动员是不合适的，这一标准违反了排他性原则，因为某个学生可能是男生的同时又是运动员，他占据了两个分类项次。再如，把学生分成中学生和大学生在有些情况下也不一定合适，该标准违反了普适性原则，即有些学生既不是中学生也不是大学生（如小学生）。
表示分类的名词：
种：kind, sort, type
类：group, classification, category
组成成员：member
分部/分支：division/branch
纲：class 目：order 科：family 属：genus 种：species
表示分类的动词和动词短语：
将……按……分类（排序）：class, classify, divide, categorize, group, place, arrange 属于某一类：belong to, fall into, be classed with
包括若干类：there be, contain, consist of, comprise, include, be composed of, be comprised of
组成……类：make up, constitute, compose
E x e r c i s e s
1. Read the following passages and discuss whether they follow the classification criterion of exclusiveness and inclusiveness.
Passage 1:
generation of electricity to meet the power and light needs of cities and industries. The other covers the application of small amounts of power for communication and various other purposes.
Passage 2:
We usually think of bees as being sociable insects which live in communities, but this is not always true. One way of classifying bees is by “social” and “solitary” species, and there are many of the latter. Bumble bees（野蜂）and honey bees are social species. Among solitary bees there are primitive wasplike bees, medium-sized solitary mining bees, so-called sweat bees, \carpenter bees and cuckoo bees.
2. Read the following passage, and fill in the blanks with appropriate words.
In Britain, state schools can be classified according to the age range of the pupils and the type of education provided. Basically, there are two types of schools: primary and secondary. Primary schools cater to（满足需要）children age 5-11 and secondary schools ages 11-16 (and up to 19). Primary schools can be sub-divided into infant schools (for age 5-7) and junior schools (for age 7-11). Secondary schools may be one type for all abilities, viz.（即）comprehensive schools; most secondary schools are of this kind. Alternatively, pupils may be grouped according to their ability and selected by means of an examination at age 11 (known as the“11-plus exam”). Thus, grammar schools cater to those with academic ability; modern schools for those with less academic ability; and technical schools for those with more practical skills.
1) Schools _________________________________________ the pupils’ages and the
types of education.
2) There are ________________________________________ schools: primary and
secondary.
3) Primary schools ___________________________________________ into infant and
junior schools.
4) Secondary schools pupils ______________________________ their ability.
5) The criterion（标准）for classifying secondary schools is whether or not there is
______________________________.
2. There are thousands of languages in the world. Languages are classified into
