Special circumstances
Collective nouns
Collective nouns such as "group" or "team" are treated as singular in the plural, e.g., "groups" or "teams".
Compound nouns
Possessive case is used to show ownership or possession. It is formed by adding an apostrophe and an 's' to the end of the noun. For example, "John's car" means that the car belongs to John.
Some nouns ending in -e do not change in the plural, e.g., "knife" -> "knives".
Weak nouns ending in -o
Nouns with a final -o often add -s in the plural, e.g., "piano" -> "pianos".
Usage
Uncountable nouns are usually used without a determiner (e.g., "I need more furniture.").
02
The plural form of English nouns