By Clare Dodd, 26 May 2015, http://wiki.d-addicts.com/Noble,_My_Love
English books and pencils: which or that
Which word should I use? Is it which or that? Both of these words are pronouns, and both are used to identify a person, place, thing or thought.
Their misuse is one of the most common mistakes in business and technical writing, and it’s easy to get them confused. However, the rules for which sentences use that are simpler than you’d think. It all comes down to the type of clause they refer to (obviously!).
Restrictive clauses and that
A restrictive clause is an element of a sentence that can’t be removed without changing the sentence’s meaning.
Products that are poorly design make me sick.
Without the clause ‘are poorly designed’, the meaning changes to suggest the speaker hates all products. Thus, ‘are poorly designed’ is a restrictive clause.
Use ‘that’ in conjunction with restrictive clauses.
Non-restrictive clauses and which
A non-restrictive clause is an element of a sentence that can be removed without changing the sentence’s meaning. It adds description or detail.
The toner, which I purchased yesterday, is in the office supply closet.
In this case, you can remove ‘which I purchased yesterday’ without losing the sentence’s intention. It is non-restrictive. This is also called a relative clause.
The toner is in the office supply closet.
Use which for non-restrictive clauses. Notice that a comma comes before which, unless the phrase ‘in which’ can be used.
The closet in which we keep the toner is locked.
Removing the non-restrictive clause gives us:
The closet is locked.
Examples of which sentences use that (and those sentences that use which)
The company that arranges our travel is closed for the holiday; I’ll have to book your flight next week.
The sales team, which has a new member, is about to launch a new ad campaign for our mobile app.
The report in which the data can be found is saved in the shared drive.