You should write it's mine, with an apostrophe. It's is the contracted form of it is – the apostrophe represents the missing i in the same way that an apostrophe is used to represent the missing o in don't , and the missing a in we're.
But why is its mine – without an apostrophe - incorrect? Let's imagine the question.
- Whose is this coat?
We can answer with a long form:
• It is my coat.
Or we can use a contraction:
• It's my coat.
It's is the short form of it is. The idea of possession is
in the possessive adjective my.
We can answer with a shorter form:
• Whose is this coat?
• It's mine.
Mine is a possessive pronoun and here it means my coat. In fact you can make the answer even shorter like this:
• Whose is this coat?
• Mine.
This works as an answer because the idea of 'possession' and 'coat' are both contained in the word mine. The word it's does not contain the idea of possession in the phrase it's mine .
But let's imagine for a minute that your pet dog has a coat – this is
quite common in some cold countries – and you are asked the same
question.
- Whose is this coat?
We can answer with a long form:
• It's the dog's coat.
Or we could say
• It's the dog's.
Remember, it's is the short form of it is .
The idea of possession is in the possessive adjective the dog's.
But we could use a possessive pronoun if we wanted to answer with an even shorter form:
• Whose is this coat?
• It's its.
So its (no apostrophe) is a possessive pronoun and here it means the dog's coat. It isn't a contraction – it doesn't mean it is. But most native English speakers would probably feel uncomfortable saying it's its – and would prefer to say it's the dog's instead.
Words like mine and its are possessive pronouns, and they are never written with apostrophes. We use them to say that something belongs to someone. If the coat belongs to you, I could say it's yours. Here is a table to help you:
Of course when we want to talk about possession without using adjectives and pronouns, we need to use a possessive 's – with an apostrophe – like this:
It's Peter's coat
It's the footballers' changing room
It's the dog's ball
It's the box's lid
But if we replace the nouns with pronouns, we lose the apostrophe.
It's Peter's coat – it's his
It's the footballers' changing room – it's theirs
It's the dog's ball – it's its
It's the box's lid – it's its
But remember, we don't usually say it's its.
But why is its mine – without an apostrophe - incorrect? Let's imagine the question.
- Whose is this coat?
We can answer with a long form:
• It is my coat.
Or we can use a contraction:
• It's my coat.
It's is the short form of it is. The idea of possession is
in the possessive adjective my.
We can answer with a shorter form:
• Whose is this coat?
• It's mine.
Mine is a possessive pronoun and here it means my coat. In fact you can make the answer even shorter like this:
• Whose is this coat?
• Mine.
This works as an answer because the idea of 'possession' and 'coat' are both contained in the word mine. The word it's does not contain the idea of possession in the phrase it's mine .
But let's imagine for a minute that your pet dog has a coat – this is
quite common in some cold countries – and you are asked the same
question.
- Whose is this coat?
We can answer with a long form:
• It's the dog's coat.
Or we could say
• It's the dog's.
Remember, it's is the short form of it is .
The idea of possession is in the possessive adjective the dog's.
But we could use a possessive pronoun if we wanted to answer with an even shorter form:
• Whose is this coat?
• It's its.
So its (no apostrophe) is a possessive pronoun and here it means the dog's coat. It isn't a contraction – it doesn't mean it is. But most native English speakers would probably feel uncomfortable saying it's its – and would prefer to say it's the dog's instead.
Words like mine and its are possessive pronouns, and they are never written with apostrophes. We use them to say that something belongs to someone. If the coat belongs to you, I could say it's yours. Here is a table to help you:
| Possessive adjectives | Possessive pronouns |
| It's my coat | It's mine |
| It's your coat | It's yours |
| It's his coat | It's his |
| It's her coat | It's hers |
| It's its coat | It's its |
| It's our coat | It's ours |
| It's your coat | It's yours |
| It's their coat | It's theirs |
It's Peter's coat
It's the footballers' changing room
It's the dog's ball
It's the box's lid
But if we replace the nouns with pronouns, we lose the apostrophe.
It's Peter's coat – it's his
It's the footballers' changing room – it's theirs
It's the dog's ball – it's its
It's the box's lid – it's its
But remember, we don't usually say it's its.
