It’s easy to see why these terms cause confusion, though, as they sound very similar when spoken. As such, make sure your writing is always clear by keeping the following uses in mind.
There (In That Place)
‘There’ has two main uses. The most common is to mean ‘that place’, such as in:
The piano is over there.
In this case, ‘there’ indicates the position of something (‘the piano’).
We typically use ‘there’ when referring to something at a distance, with ‘here’ used for things that are nearby.
The second use of ‘there’ is to emphasise the truth or existence of something, usually by saying either ‘there are’ or ‘there is’:
There are many people who enjoy dancing.
There is a reason that I love to dance.
This is known as the ‘there transformation’, which changes the construction of a sentence. These sentences could be rewritten without ‘there’, but they sound different if we do this:
Many people enjoy dancing.
I love to dance for a reason.
‘There is’ is also sometimes shortened to ‘there’s’, but this is usually considered informal.
Their (Belonging to Them)
‘Their’ is a plural possessive determiner, which means we use it to indicate that something belongs to a group of people:
The musicians picked up their instruments and started to play.
Here, the use of ‘their’ shows that the instruments belong to the musicians.
‘Their’ can also be used in some situations to indicate that something belongs to a single person whose gender is unknown or indeterminate:
Somebody left their glasses in the bar last night.
But this is considered incorrect by some, so in formal writing you may want to use ‘his or her’ instead (e.g. ‘Somebody left his or her glasses in the bar last night’).
They’re (They Are)
Finally, ‘they’re’ is short for ‘they are’. As such, we only use it when ‘they are’ would also apply:
They’re a great live band! = They are a great live band!
However, as with other contractions, ‘they’re’ could be seen as informal, so you’re usually better off using ‘they are’ in formal writing.
There, Their or They’re?
As long as you remember that ‘they’re’ is short for ‘they are’ (the apostrophe is a good clue), it should be easy to avoid confusing this term with the other two in this trio.
‘There’ and ‘their’ are trickier, since they are quite similar on paper. The best advice we can give is to keep in mind that ‘there’ contains the word ‘here’, which also refers to a place. Remember:
There = In that place
Their = Belonging to them
They’re = Short for ‘they are’