Do not confuse there, their, and they're. That would be a serious mistake.|
They're is short for they are.
Their shows possession. It's just like my, his, her, and our.
There is a place. It's similar to here.
They're, Their, and ThereDo not confuse they're, their, and there. A mistake involving these constitutes a grammatical howler.
They'reThey're is a shortened version of they are. (The apostrophe replaces the letter a.) Only use they're if you can substitute it with they are.
This is wrong – should be their
(office sign by sink)
TheirTheir is used to show possession. It is just like my, your, his, her, its, and our. (These are called possessive adjectives.) Here is a little trick: use the word our instead of their. If the sentence still makes sense, then their is almost certainly correct. This trick works because our and their are both possessive adjectives used for plurals.
ThereThe word there is similar to the word here in that it represents a place. It has two main uses: (1) it is a specified place (like in the first example below), and (2) it is an unspecified place (like in the second example). Also, like in the second and third examples, the word there can be used to show that something exists.
NOT IN FORMAL LETTERS
As a general rule, try to avoid words like they're and doesn't in formal letters. Always expand them to they are and does not.
(See lesson Apostrophes.)