Restrictive and Non-restrictive Clauses

Which and that both introduce clauses (groups of words) that provide more information but are not grammatically necessary to the sentence.

• e.g., The daily special, which was poached salmon, cost a lot.
• e.g., The dish that the sous-chef prepared turned out to be better than the daily special.

Use that when the information in the clause is necessary to the meaning of the sentence. It’s called a restrictive clause because it limits or affects the purpose of the sentence.

• e.g., Suitcases that weigh more than 23kg must be checked.
  • that weigh more than 23 kg is necessary to the purpose of the sentence. If you removed this restrictive clause, it would imply that all suitcases must be checked, which isn’t what the author intends.
• e.g., Drinks that have caffeine make it hard to fall asleep.
  • that have caffeine is also restrictive. If you take this part out, it suggests that all drinks make it hard to fall asleep.

Some writers will use which for a restrictive clause instead of that. This is technically fine, but if you are having any confusion about the distinctions between restrictive and non-restrictive clauses, it is better to maintain a clear distinction between that and which, for clarity’s sake.

Use which when the information in the clause is not necessary to the meaning of the sentence. It might be helpful or interesting, but if you took it out, the sentence would still make sense.

• e.g., The suitcase, which was stuffed with dirty clothes, didn’t fit in the overhead bin.
  • If which was removed: e.g., The suitcase didn’t fit in the overhead bin.
• e.g., Coffee and tea, which both have caffeine, are Canada’s favourite morning drinks.
  • If which was removed: e.g., Coffee and tea are Canada’s favourite morning drinks.

Note that the non-restrictive which clause is set off by commas.

Use that without commas for a restrictive (necessary) clause. That is required more often than which. Use which with commas for a non-restrictive (not necessary) clause.

Write in that (for restrictive clauses) or which (for non-restrictive clauses).

1. The spoon __________ fell on the floor needed to be washed.
2. The book __________ she wanted was on the top shelf.
3. They used Post-It notes __________ come in various colours to organize the pages.
4. For the hike I need shoes __________ are sturdy.
5. For the hike I need sturdy shoes __________ are expensive.
6. The first skyscraper we saw __________ was the biggest one on that street had 67 floors.
7. The only elevator __________ went all the way to the top was out of service.
8. The cord __________ charges this computer is missing.
9. He provided us with a whole box of samples __________ we didn’t really need so we could make a decision.