1. One form instead of a whole phrase
Imagine two bags: the other person already knows what you are comparing. Instead of repeating my bag, say mine. This is not an abbreviation of bag or a replacement for any final word. Mine replaces the entire possessive noun phrase: my bag, my old bag or my bags, depending on context.
Some languages change possessive forms according to the gender or number of the thing possessed; English uses mine in all these cases. The English form shows whose thing it is but does not itself identify what the thing is. That must be clear from the conversation or situation.
The full phrase is also correct: This is my bag and This is mine can describe the same bag. Choose mine when there is no need to repeat the noun. If the thing has not been mentioned and is not visible, explain what you mean first.
my bag / my old bag / my bags → mine, when the thing is clear from context
Your bag is new. Mine is old.
Your bag is new. Mine is old.
Mine = my bag. The second sentence does not repeat bag; old describes the bag.
I have my old bag. You can use mine.
I have my old bag. You can use mine.
Mine refers to the bag already mentioned. The pronoun does not mean that the bag has lost the characteristic old.
2. Choose according to the owner, not the thing
The six main pairs are my → mine; your → yours; his → his; her → hers; our → ours; their → theirs. Use mine for something belonging to me, yours for something belonging to the person I address, and ours for something belonging to us. For a previously mentioned person referred to as he, use his; for she, use hers; for they, use theirs.
Yours can address one person or a group. Ours includes the speaker among the owners; theirs does not include the speaker in that group. In a dialogue, the same object can be mine for one speaker and yours for another.
Do not guess his or hers from a name, profession or the appearance of an object. Use the known owner and the pronouns used for that person.
She has a green cup. The green cup is hers.
She has a green cup. The green cup is hers.
Hers is chosen because of she, not cup: the English word cup does not determine the owner's gender.
We have one room. This room is ours.
We have one room. This room is ours.
Ours shows that the room belongs to, or is assigned to, a group including the speaker; there is one room.
You both have tickets. Are these yours?
You both have tickets. Are these yours?
Addressing two people does not change the form yours.
3. My before the noun, mine instead of the phrase; the special form his
My, your, her, our and their are possessive determiners: they introduce a noun phrase. Adjectives can come between the determiner and noun: my old bag, her blue coat. Mine, yours, hers, ours and theirs already represent that phrase, so do not put them before its head noun: not mine bag, but my bag or mine.
His has the same spelling in both roles: his desk and The desk is his. Identify the role from the construction, not simply from the letter s. Her can also be a personal object pronoun in I know her; that means the person herself, not something belonging to her.
The rule does not forbid every noun appearing later in the sentence. In Mine is on the table, table belongs to another phrase: on the table. The error arises specifically when mine is used as a determiner in mine bag.
His desk is clean. Mine is on the left.
His desk is clean. Mine is on the left.
His introduces desk; mine represents my desk on its own. Left in the following phrase does not change that role.
Our room is bigger than yours.
Our room is bigger than yours.
Our is the determiner with room. Yours replaces your room. This sentence does not contain ours.
I can see her. The red coat is hers.
I can see her. The red coat is hers.
Her refers to the person being seen; hers expresses that the coat belongs to that person.
4. Not only after is and not only at the end
A possessive pronoun can be a subject: Mine is blue. It can be an object after a verb: Take mine. It can follow be: The blue one is mine. Its form does not change with this role.
In a simple comparison, the pronoun avoids repeating the noun: My room is smaller than yours. This compares my room with your room, not me with you.
To check the meaning, mentally expand the pronoun into the full phrase. If You can use mine means You can use my pen, the form must be mine, not me: the thing being used is the pen, not the person.
My phone is here. Yours is in the kitchen.
My phone is here. Yours is in the kitchen.
Yours = your phone and serves as the subject at the beginning of the sentence.
Her bike is small. I use hers.
Her bike is small. I use hers.
Hers = her bike after use. Moving to the object position does not turn hers into her.
Their table is longer than ours.
Their table is longer than ours.
Ours = our table: the comparison is between two tables, not two groups of people.
5. The form stays the same; is or are depends on the things
For one thing or several, the pronoun is unchanged: This key is mine; These keys are mine. Do not add a plural ending to mine or remove s from hers, ours or theirs because there is only one thing.
When a possessive pronoun is the subject, make the verb agree with what it replaces. For one shared desk: Ours is near the door. For several of our chairs: Ours are near the door. There are several owners in both cases, but desk or chairs determines is or are.
If number is not clear from context, theirs alone is not enough to choose is or are. First establish whether one thing or several things are meant.
We have a desk. Ours is near the window.
We have a desk. Ours is near the window.
Ours = our desk: one thing, so use is, even though we refers to several people.
She has two bags. Hers are under the chair.
She has two bags. Hers are under the chair.
Hers = her two bags: there are two things, so use are, even though there is one owner.
6. No apostrophe and no extra ending
Learn the complete forms: mine, yours, his, hers, ours, theirs. None has an apostrophe. The s in yours or hers is part of the pronoun, not a plural marker or the possessive 's added to names.
Mine does not become mines, and his does not become hiss or his's. Do not build these forms by mechanically adding s to every word; learn my–mine and the unchanged pair his–his.
In It's hers, the apostrophe belongs to It's = It is. It does not appear in hers. Distinguish the contracted verb from the possessive pronoun.
These tickets are theirs.
These tickets are theirs.
Theirs is written as one word without an apostrophe. Plural tickets does not add anything to theirs.
It's his.
It's his.
It's contracts It is; his already has the required form and needs no extra s.
7. Asking, clarifying and offering
Is this yours? and Are these yours? check whether something belongs to the listener. Whose bag is this? is an open question about ownership. Mine is a possible conversational answer because the thing has already been named; It's mine is fuller.
Change the viewpoint in your reply: someone asks Is this yours?, and you confirm It's mine. If speaking for your group, you can answer It's ours. Do not automatically copy yours from the question.
Ownership is not permission. It's mine only states whose thing it is. You can use mine also offers permission to use it. To deny a mistaken assumption, say It isn't mine; to clarify politely, say Excuse me, is this yours?
Are these yours? — Yes, they're mine.
Are these yours? — Yes, they're mine.
The question concerns several things; they refers back to them in the reply, while mine identifies the person answering as the owner.
I need a pen. — You can use mine.
I need a pen. — You can use mine.
The second remark both identifies the owner and gives permission; pen does not need to be repeated.
8. Boundaries: useful to recognise without overcomplicating the topic
Their and theirs can refer to one person as well as a group when that person is referred to as they, including when gender is unknown. This is not a plural-agreement mistake. In the basic exercises, the owner is identified clearly enough that there is no need to guess his or hers.
Independent its, as in The bowl is its, is usually avoided: The bowl is the dog's is simpler. However, do not conclude that its can never occur without a following noun: of its own is an established construction. This is a separate boundary, not a seventh form for ordinary short answers.
A friend of mine means one of my friends. Mine still expresses a possessive relationship, but the whole phrase with of has a separate structure. Recognising it is enough for this lesson: the main practice is identifying ownership, replacing a repeated phrase and responding appropriately.
For your own answers, compare your text with the model and criteria: is the thing clear, is the owner correct, is the form correct and is the intended purpose achieved? The model is one possible version; self-checking is not an automatically validated assessment or certification of your level.
Someone left a hat here. This must be theirs.
Someone left a hat here. This must be theirs.
Theirs refers to one unknown person represented by someone; there is no need to assign that person a gender.
The dog has a bed of its own.
The dog has a bed of its own.
Of its own is a separate established construction; do not transfer it to an answer consisting only of its.
A friend of mine lives here.
A friend of mine lives here.
Mine belongs to of mine; this is not the incorrect determiner pattern mine friend.
Common mistakes
Incorrect:This phone is my.
Correct:This phone is mine.
My cannot represent the entire phrase my phone on its own; to avoid repeating phone, use mine.
Incorrect:I use hers bike.
Correct:I use her bike.
Before the head noun bike, use the determiner her. An alternative avoiding repetition is I use hers.
Incorrect:Those keys are mines.
Correct:Those keys are mine.
The possessive pronoun mine does not form a plural with -s; several keys are still mine.
Incorrect:This seat is your's.
Correct:This seat is yours.
The possessive pronoun yours has no apostrophe.
Incorrect:Our bags is here.
Correct:Our bags are here.
Bags is plural. The same agreement must remain when our bags becomes ours: Ours are here.
Incorrect:The blue cups are her.
Correct:The blue cups are hers.
Without the noun, ownership of the cups is expressed by hers, not the personal form her.