Meaning of -'S in English

-'S

I. -'s 1 /z, s/ BrE AmE

1 . the short form of ‘is’:

John’s here.

What’s that?

She’s writing a letter.

2 . the short form of ‘has’:

Polly’s gone out.

A spider’s got eight legs.

3 . a short form of ‘us’ used only in ‘let’s’

4 . spoken a short form of ‘does’, used in questions after ‘who’,‘what’ etc that many people think is incorrect:

How’s he plan to do that?

II. -'s 2 BrE AmE suffix

1 . forms the ↑ possessive of singular nouns, and of plural nouns that do not end in -s:

my sister’s husband

Mary’s generosity

yesterday’s lesson

the children’s bedroom

2 . British English the shop or home of someone:

I bought it at the baker’s (=at the baker’s shop) .

I met him at Mary’s (=at Mary’s house) .

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.