Plurality falls under the concept of grammatical number. So, one prefaces the discussion of plurality with a brief overview of grammatical number. Since this entry is written in English, one can consider grammatical number in English.

English nouns are either plural or singular, which is usually signaled by the presence or absence of the inflectional ending s. Thus, book (singular) contrasts with books (plural). However, some nouns have peculiar forms for singular and plural. For example, the plural of louse (singular) is lice (plural). Some nouns, like deer, do not take the suffix s, yet behave as both singular and plural. This is shown by the form of its preceding determiner and, should the noun be in the subject position, by the form of the main verb. Thus, in the sentence That deer is crossing the road, deer behaves like a singular noun, while...