Which and that
'That' is often overused and in many cases can be left out.
Bear in mind 'that' and 'which' are not interchangeable terms.
Changing them can alter the meaning of a sentence.
'That' is used to introduce restrictive clauses - information that is vital to the point of a sentence.
Restrictive clauses do not have commas around them. Non-restrictive clauses do.
✔ Our office that is on the fourth floor needs painting.
✔ Our office, which is on the fourth floor, needs painting.
In the first example, using 'that' suggests we have more than one office.
In the second example, using 'which' suggests we only have one office.
Last updated: 27 June 2017