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Note 102 – Do you need a comma before which?

This blog is about clauses that are introduced by the word which and the rules around commas when the clause follows a noun.

As this can get a little confusing, first you need to decide if the clause that follows which is either “used to introduce crucial identifying pieces of information” or “used in clauses that give purely incidental information”, explains Martin Manser and Stephen Curtis in the Pocket Writer’s Handbook.

From the research I have carried out today, I have come up with the following different sentence formations:

  1. [Noun] [which (or that) + crucial information about the sentence] [rest of sentence]
  2. [Noun] [which (or that) + crucial information about the sentence]
  3. [Noun], [which + information that is added as an extra], [rest of sentence]

Important note: you never use that in sentence formation 3

Explanation of sentence formations 1 and 2 above (with examples)

You can use either which or that to introduce these types of clauses (although that is more commonly used). No commas should be used before and after the which (or that) clause. Strunk & White call these restrictive clauses as they define the noun and cannot be split into two different statements (William Strunk and E.B. White, The Elements of Style). Here are some examples:

  1. Buckets which (or that) have holes in cannot hold water.
  2. I like the house that (or which) stands on the hill.

Explanation of sentence formation 3 above (with examples)

You can only use which to introduce these types of clauses. Sentences in these cases still makes sense without the which clause, therefore bracketing commas must be used to isolate this information (for more on bracketing commas please refer to my note 3 – the use of brackets and bracketing commas). Strunk & White call these non-restrictive clauses as they “do not limit or define, they merely add something”. The sentence could be split into two different statements. Here are some examples:

1a) The following sentence, which was all I could think of at such short notice, explains this example well.

(Split into two sentences: The following sentence was all I could think of at such short notice. It explains this example well).

1b) The train, which was ten minutes late, got us to our destination five minutes before we needed to.

(Split into two sentences: The train was ten minutes late. It got us to our destination five minutes before we needed it to).

That’s it for today. I’d like to thank my work colleagues for giving me something to blog about today. I think they were worried that this blog may be a little boring, so I tried to make it as interesting as I could.

Don’t forget that you can subscribe to receive my blogs daily by email so that you don’t miss any. Just click ‘sign me up’ on the home page.

Until tomorrow…


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My website: (includes the introduction to my upcoming book ‘A Gift for Stressed and Busy Parents’)

Twitter: @madeirasandra and @tipsandluxuries

Reference list:

The Pocket Writer’s Handbook by Martin Mander & Stephen Curtis (Penguin Reference Library)

William Strunk Jr. and E.B. White The Elements of Style, fiftieth anniversary edition (2009), USA


About Sandra Madeira

I am a full-time working mum with a passion for writing and inspiring others. Subjects I tend to blog about are life skills, parenting, decluttering, worklife balance, etc. At the moment I am on a decluttering mission creating space in my house, garden and mind. I have challenged myself to do at least ten minutes a day and write about it. Have a good day! Sandra Freelance Writer


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