The following sentences are from the BBC [just to give a source showing that these sentences are all grammatically correct].

  1. It was Rob that/who ate my biscuits. (not Catherine)
  2. It was my biscuits that/which Rob ate. (not my sandwiches)
  3. Was it Rob that/who ate my biscuits?

The list could goes on. My point is, these relative clauses are not defining relative clauses.

In a defining relative clause, we have an antecedent and a relative clause where the relative clause helps the listener identify who or what the antecedent refers to:

  1. That's the man who ate my biscuits.
  2. Look for the elephant who's carrying the umbrella.
  3. The doctor that treated me was a woman.

In (4) the phrase who ate my biscuits tells us which man we are talking about. The clause who's carrying an umbrella identifies which elephant to look for. The clause that treated me helps identify which doctor was a woman. And we see also that in some sense the relative clause restricts our interpretation of the antecedent. For these reasons, such clauses are also sometimes referred to as 'restrictive'.

Because of the way these work, we cannot use such relative clauses when the antecedent is already known or identifiable. For example (7) below only works if you have more than one father:

(7) Yesterday, I met your father that bought me a drink.

Further information

I've been told in comments that grammars like CGEL, which recognise that these types of clause in (4-6) are normally defining/restrictive, call them 'integrated' relative clauses. They note that integrated relatives form a constituent with antecedent noun phrases, and are tightly integrated into the construction they appear in.

However, as @BillJ and others inform me, the relative clauses in (1-3) do not form a constituent with their antecedent.

The question

Back to the thrust of my question. In (1-3), the relative clauses do not explain or define who Rob is. The listener already knows who Rob is. So unlike the defining relative clauses in (4-6),they do not restrict our understanding of the reference of the noun phrase Rob. And as shown in (7) unlike with defining/restrictive/integrated relative clauses we can use the relative clauses in (1-3) with a name or proper noun whose identity is already established.

As I understand it, it's usually ungrammatical to use 'that' in a non-defining relative clause. Given that the relative clauses in (1-3) are not defining, are not restrictive, and do not form a consituent with their antecedent, why is using that not a problem when the relative clause is in a cleft sentence?

Also aren't these relative clauses providing extra information?+

Edit note:

+In my original question I assumed that these relative clauses in (1-3) provide additional information. However, as pointed out in comments and in @DW256's answer, they aren't.

  • Why is sentence 2 in your list? No who substitution there.
    – nnnnnn
    Aug 27, 2022 at 22:15
  • @nnnnnn As you mentioned, there is 'that' used instead of 'who' which is a substitution; this is why it is in the list...
    – user442526
    Aug 27, 2022 at 22:41
  • Why do you say that these are nondefining relative clauses? Many people would say that they are defining. Aug 27, 2022 at 22:47
  • 1
    I prefer that for which in restrictive clauses, but not instead of who. In #1, you want to use that for who, which I wouldn't do. Aug 28, 2022 at 0:52
  • 1
    1) Everyone needs to stop arguing in the comments. (Some of what's been said should be made into its own answer). 2) I'm not locking edits. The old revisions are there if we really need them.
    – Laurel
    Aug 29, 2022 at 13:20

1 Answer 1


Note that it would be questionable to put a comma after the foregrounded element in the clefts. With a supplementary relative clause, this is always possible and usually advisable.

? It was Rob, that/who ate my biscuits.

? It was my biscuits, that/which Rob ate.

? Was it Rob, that/who ate my biscuits?

Clefts are an information packaging construction, which means that they are different ways of stating:

Rob ate my biscuits.

His eating of the biscuits in the canonical version is not supplementary information, so, although possibly non-defining, it should not be viewed as supplementary in the cleft construction.

There are four types of relative clauses:

The man who won died several days later. [integrated]

Her mother, who we haven't seen in years, attended the party as well. [supplementary]

It was Rob who ate my biscuits. [cleft]

What he wanted was a fresh start. [fused]

  • 1
    It would also be useful to mention that the relative clause in a cleft is not a modifier. It does not form a constituent with its antecedent.
    – BillJ
    Aug 28, 2022 at 6:53
  • Thank you DW256. The problem is if you use a comma you can't use 'that' in this sentence: 'It was Rob, that/who ate my biscuits'. Because it is incorrect to use commas if it's not an extra information clause and if it's an extra information clause it's wrong to use 'that' as a substitution for who. See unit 95 (p.190) in English Grammar in Use, Murphy (5th edition). This is mutually exclusive.
    – user442526
    Aug 28, 2022 at 15:05
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    @orhantorun Exactly - it's not an 'extra information clause', which is made clear by the general inadmissibility of the comma in clefts, and hence there is no restriction against using 'that'.
    – DW256
    Aug 29, 2022 at 3:51
  • @orhantorun I suggest you take on board what DW256 tells you. The clauses are defining; they are an essential part of the information being conveyed. They are not modifiers as such, but they are dependents, thus integrated, into their respective matrix clauses. There is no such thing as a non-defining relative clause in a cleft construction.
    – BillJ
    Aug 29, 2022 at 7:48
  • @BillJ These are not defining - as DW256 has admitted may be the case in their post! These are "defined" relative clauses where the function of the so-called antecedent and the relative clause are reversed! That's why we can use names as so-called antecedents here. Aug 29, 2022 at 9:10

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