What’s the difference between ‘who’ and ‘that’?
That’s a good question, and here’s a rule for you: use ‘who’ when you are talking about people, and ‘that’ when you are talking about things.
And that’s the end of the lesson!
Except it isn’t, because things are a little more complicated than that.
Because ‘that’ can actually represent people too, and has been used in this way by a host of famous writers down the years. So, if your high school English teacher told you to live by the rule as mentioned above, then he or she was actually a little wide of the mark.
‘Who’ is a relative pronoun, as is ‘which’. It is definitely correct to say that ‘who’ is for when you are talking about people, and ‘which’ is for when you are talking about things. This rule is non-negotiable.
However, ‘that’ is an acceptable alternative as a relative pronoun when using both ‘who’ and ‘which’. However, ‘that’ can only be used as a defining relative pronoun, and in a defining relative clause. It cannot be used as a non-defining relative pronoun in a non-defining relative clause.
Are you confused yet?
Don’t be, because this can be explained quite simply so you never need to make this mistake again.
Defining relative clauses
Defining relative pronouns are used in defining relative clauses. Defining relative clauses are used when the subject or object needs to be defined in order to be identified. Here is an example:
‘He is the man.’
Now, the natural question this raises is, ‘who?’, because without defining this man, we have no idea who is being referenced.
‘He is the man who lives next to my sister.’
Now we can identify him (he’s the man who lives next to my sister).
Here’s another example using ‘which’.
‘This is the mug.’
But which mug are we talking about?
‘This is the mug which I use for all my hot drinks.’
Now we know!
These examples both include what are called ‘defining relative clauses’. In both of these examples, ‘who’ and ‘which’ can be replaced with ‘that’, because the pronoun is defining. So:
‘He is the man that lives next to my sister.’
‘This is the mug that I use for all my hot drinks.’
So, to answer the original question, there is no difference between ‘who’ and ‘that’ when the relative pronoun is defining.
Non-defining relative clauses
But relative clauses are not only used to define something. They can also be used to add information.
In this case, ‘who’ and ‘which’ are still distinguished by whether they are adding information about a person or a thing.
‘My brother, who is a keen runner, lives a healthy lifestyle.’
‘My car, which is a Ford, is red.’
Now, the commas are a bit of a giveaway. That’s because everything included inside those commas is simply additional information that (which) is not required to define the subject of the sentence. If you removed those clauses, the sentences would still make sense:
‘My brother lives a healthy lifestyle.’
‘My car is red.’
It is also important to remember that the words ‘who’ and ‘which’, in the original non-defining relative clause examples, cannot be replaced with ‘that’. So:
‘My brother, that who is a keen runner, lives a healthy lifestyle.’
‘My car, that which is a Ford, is red.’
This simply doesn’t work, and the standard ‘who’ and ‘which’ must be used.
So, to answer the original question once again (what is the difference between ‘who’ and ‘that’?) the answer is that ‘who’ is for when you are talking about people, and ‘that’ is nothing!
So, it really all comes down to whether it’s a defining relative pronoun, or not!