The personal pronouns are declined as follows:

Note:

No pronoun uses an apostrophe for its possessive form as nouns do. This includes the third person, singular, neuter pronoun its. It’s with the apostrophe is the contraction of it is.

In the possessive case, my, thy, her, our, your, and their are used when the noun is expressed.
The pronouns mine, thine, hers, ours, yours, and theirs are used when the antecedent noun is understood.

For example

That book is yours; this is mine.
That book is your book; this is my book.

When mine, thine, hers, ours, yours, and theirs are used, they perform double office.

• First, they represent the speaker, the hearer, or the person spoken of as the possessor.
• Second, like other limiting or qualifying words, when the noun is understood, they represent that noun, not as a pronoun does, but as an adjective.

For example

This [book] is arithmetic, that [book] is a geography.
The violent [persons]take it by force.
Mine [my task] was an easy task.

Properly, none of the above italicized words are nouns. The first three are adjectives that limit the understood nouns that follow them. The last, mine, is a possessive case personal pronoun used to limit the understood noun phrase, my task.

If this, that, or violent are used as nouns, then so is the word mine. It is then, strictly, a pronoun, not in its pronominal use, but as an adjective.  It may, like an adjective, be parsed as a noun, in the nominative or the objective case.