Meaning of -'S in English

-'S

s after vȯiceless consonant sounds other than s, sh, ch; z after vowel sounds or vȯiced consonant sounds other than z, zh, j; ə̇z after s, sh, ch, z, zh, j noun suffix or pronoun suffix

Etymology: Middle English -s, -es, gen. singular ending of nouns, from Old English -es, gen. singular ending of some masculine & neuter nouns; akin to Old High German -es, gen. singular ending of some masculine & neuter nouns, Old Norse -s, Gothic -is, Greek -ou, Greek (Homeric) -oo, -oio, Sanskrit -asya

— used to form the possessive of singular nouns

boy' s

of plural nouns not ending in s

children' s

of some pronouns

anyone' s

and of word groups functioning as nouns

the man in the corner' s hat

or pronouns

someone else' s

Webster's New International English Dictionary.      Новый международный словарь английского языка Webster.