Plural
A plural noun is one which by addition of an ending (in English, French, Spanish and Portuguese usually s) evokes more than one referent. In most languages it is directly opposed to the grammatical category of 'singular' (for 'one') but some languages have a third category, 'dual' (for 'two') and others have even more, in which cases 'plural' is used for any larger number than those.
In most languages the plural of nouns is clearly marked; but in others, such as Japanese, it is unmarked, and nearby expressions of quantity may be needed. In English some plurals have no markers; for example "sheep" is both singular and plural.
Pronouns have lexical plurals in English, where the plural of I is we, and of he, she and it, they. The originally plural-only word you, retaining its plural verb forms (e.g. are), now does the work of the singular thou, which is only in restricted use.
Verbs have different forms according to several criteria, number being merely one of them.