Getting to grips with using ‘that’ and ‘which’

‘That’ and ‘which’ can sometimes be used interchangeably. But it’s not always correct to do so.

The general rule is: use ‘that’ to define and use ‘which’ to inform or add information.

Defining

These are the spending cuts that the Board agreed.

Here, the spending cuts in question are defined and limited to being the ones agreed to by the Board (as opposed to any others that might be enforced). It is actually not wrong to substitute ‘which’ here in British English, although American English would probably only use ‘that’.

Informing

The spending cuts, which the Board decided, have been very effective.

Here, ‘which’ introduces additional information – the people behind the spending cuts. The main point is that all the cuts being discussed here have been effective; and, incidentally, they were (all) decided by the Board. Note the two commas necessary when using ‘which’ this way: the additional information within them could be removed and still leave a full sentence.

Only ‘which’ can be used for this purpose. It’s incorrect to use ‘that’ when introducing extra information.

Punctuating

Although it is not wrong to use ‘which’ in place of ‘that’ to define or limit something, you have to be careful how you punctuate around it.

There has been very positive customer feedback on the new desserts which are made with dark chocolate.

With no comma before it, this ‘which’ is being used to define and limit the desserts which had good feedback as the ones made with dark chocolate. There are probably other flavours of dessert, but the response to those may have been less upbeat.

There has been very positive customer feedback on the new desserts, which are made with dark chocolate.

With a comma before it, this ‘which’ is being used to inform (the second comma has been replaced with a full stop). The part of the sentence after the comma is additional information about the first part. This means that all the new desserts had positive feedback and, by the way, they are all made with dark chocolate.

As you can see, altering punctuation even slightly can change the meaning of your sentence and could result in you accidentally misleading your reader.

Would you like more help with grammar? Have a look at our Essential grammar and punctuation training.