Commas in relative clauses

Cristina has written to ask how we use commas in relative clauses

So here are two very easy easy things to remember

1) Compare:

  • A) The place where I went to school is a wonderful town. and …
    B)B) Edinburgh, where I went to university, is a beautiful city.

In A you can’t say “The place is a wonderful town” … why? Because we don’t know which place it is. This means that it is essential to put the complete defining clause because “The place where I went to school” is the SUBJECT of “is” in “is a wonderful town” (grammatically this is called a Defining Relative Clause …. so we DO NOT USE COMMAS)

In B it IS possible to say “Edinburgh is a beautiful city” and “where I went to university” is extra information that grammatically is not necessary. Both parts are grammatically complete sentences (grammatically this type of Relative Clause is called a non-defining Relative Clause, because it does NOT define the subject, it only adds information, this type IS written with COMMAS at the beginning and end)


  • My brother, who lives in New York, is a doctor.
  • (I only have one brother and he is a doctor. “lives in NY” is additional information)
  • My brother who lives in London is an architect.
  • (I have more than one brother: the one who lives in London is an architect “my other brother is a teacher

2) Connecting two phrases into one at the end:

A) “Mary ate 4 big cakes, which made her feel sick“.

Here it is not the cakes that made her feel sick, it was the fact that she ATE 4 cakes that made her feel sick ..

B)B) Ian pushed Cristina into the swimming-pool, which Mariona thought was very funny

In this case “which” = Ian pushed Cristina into the swimming-pool

Again we use COMMAS (it’s the same as 2A)
C) John works for a company which makes computers. ….

Here there is NO comma because the relative clause is a DEFINING relative clause; if you just put “John works for a company” it would look a bit stupid
Do you understand when I talk about: defining and non-defining?

Defining = it defines, explains WHICH person, brother, house, place etc we are referring to.
non-defining = it doesn’t explain or define; we KNOW which one it is from other information.

Defining = no comma or commas
non-defining = comma or commas

For more English language and grammar lessons check here

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