Possessives take many forms in English.
p___ouns in the possessive case can be used as adjectives to modify nouns or stand alone as subjects, objects or complements. For example,

My book is on the table.
Mine is on the table.

I put mine in the refrigerator.

The red one is mine.
(used to modify a noun)
(used as a subject)

(used as an object)

(used as a complement)

See the table below.
p___ouns as adjectives

my
his
her
its
your
our
their

p___ouns as subjects, objects and complements
mine
his
hers
its (not common)
yours
ours
theirs

The possessive is formed by adding ?s to singular nouns and plural nouns not ending in s. Such possessives can be used as modifiers, or they can stand alone.
It is John's bicycle.
Those are the children's toys.
Jack's is the white one.
I'm going to Joe's.

With plural nouns ending in ?s, only an apostrophe (?) is used to form the possessive.
The girls' bicycles are in the repair shop.
All the students' books were stolen.

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