I was watching a video on relative clauses and there was two sentences that confused me.

"I saw a car which was white"

The speaker said this sentence is definite clause.

"She went into the apartment, which had blue walls."

The Speaker said this is indefinite.

I don't get how the last sentence is indefinite because the relative pronoun WHICH identifies the building (with blue walls) the subject went into. Therefore, it should be a definite clause, right?

  • It'd be useful to post the link to the video. Usually, you would say "I saw a white car" by limiting the relative clause to cases such as" I saw a car which was white and not blue" for purposes of differentiation. You have already posted a similar question before and you also got some answers. Why didn't you reflect on them? So for me a clear and transparent downvote!
    – user373710
    Apr 17, 2020 at 15:27
  • No, it's definite, see my answer here:link
    – BillJ
    Apr 17, 2020 at 16:26

3 Answers 3


The words used to describe these kinds of clauses vary a lot: I like Descriptive and Defining.

American English has a tendency to use “that” to introduce defining clauses, and “which” or “who” (always preceded by a comma) for descriptive clauses – I think this is a good idea – but it is not a “rule”. (In British English, this tendency is not so marked.)

As general guidance,

  1. When written, descriptive clauses are always off-set by commas.

  2. When written, defining clauses are never off-set by commas.

  3. Descriptive clauses can always be omitted because they give unimportant or unnecessary information – information that is an aside or a casual remark.

  4. Defining clauses cannot be omitted. Defining clauses tell you which precise item is being referred to.

For example:

1 Wife to her husband: “The cat that I saw yesterday is in the garden again.” – “The cat that I saw yesterday” is a single noun phrase acting as the subject, and “that I saw yesterday” defines the cat – it tells you which cat it was – it was the cat that she had seen yesterday and no other cat.

If the wife had omitted that I saw yesterday, and said “The cat is in the garden again”, her husband would have said “Which cat are you talking about? You have never mentioned a cat to me!”

2 Wife to her husband: “The cat , which I saw yesterday , is in the garden again.” = “The cat (and, by the way, I also happened to see it yesterday,) is in the garden again.” Also, the sentence assumes that her husband knows which cat it is.

If the wife had omitted , which I saw yesterday, and said “The cat is in the garden again”, it means that she is aware that her husband already knows which cat she was talking about.


"I saw a car which was white."

This would be a defining clause - there is no comma - and it might be a reply to "There are no white cars in this area."

"She went into the apartment, which had blue walls."

This would be a descriptive clause - there is a comma (and "which" has been used) - It means "She went into the apartment(that had been mentioned early) and, by the way, the apartment just happened to have blue walls, but they could have been any colour and it would not have made any difference."


First, I don't see why this speaker speaks of a sentence as being a clause: that makes no sense. Then, the terms apply to the relative clauses, strictly, and on top of that they are not "definite" nor "indefinite". On the one hand they can be called according to alternative terminologies

  •            restrictive                    /identifying          /defining        /determinative/integrated and on the other
  • descriptive/non-restrictive/non-identifying/non-defining/appositive       /supplementary (ref).
    The term "definite clause" seems to apply only to the domain of logic and programming (Wikipedia, wiktionary).

The first clause ( which was white) is a case of restrictive clause (no commas to set it apart) but this is so in BrE only. In AmE, rather formal, you use only "that" for restrictive clauses (ref.1, ref. 2).

The clause "which had blue Walls" is non-restrictive (a comma is used to set it apart from the other clause). It is not a defining clause or according to the usual terminology it is not an identifying clause: it does not identify the apartment. Here is why: you can eliminate "which had blue walls".

  • She went into the apartment.

In saying so you do not communicate any vague information, you are still referring, in the given context, to a unique apartment ; the main clause still stands correct on its own. (She went into the apartment, which happened to have blue walls.)

If the sentence had been "She went into the apartment which had blue walls." (no comma, pay attention to this difference), then suppressing the clause, you communicate imprecise information because she went into that apartment that had blue walls and not into another one; so, the apartment is not identified any more; for instance you can ask "Was it the blue walled one or was it the white walled one?".

  • 1
    I'm downvoting. You claim: "In AmE, you only use 'that' for restrictive clauses." This is absolutely untrue. There are some grammarians who say that we should only use 'that' for restrictive clauses. For informal speech, almost nobody listens to them. In formal speech and writing, some of us do and some of us don't. Sep 14, 2020 at 22:21
  • @PeterShor It is not merely for relative clauses but for restrictive relative clause; there is no explanation either about every day talk in the rule formulated by the reference: "That or Which? You may have noticed that we use ‘that’ for a restrictive clause and ‘which’ for a non-restrictive clause in the examples above. This is the standard usage in American English.".
    – LPH
    Sep 14, 2020 at 22:27
  • 1
    This is because the reference is actually wrong. Sep 14, 2020 at 22:52
  • @PeterShor Of course not, the reference isn't wrong; it's just not stipulatng "formal" and it is understood that the language level is at its best; see this other reference:dictionary.com/e/that-vs-which
    – LPH
    Sep 14, 2020 at 22:56
  • 1
    This rule was made up by prescriptive grammarians, and has never been followed in spoken English, whether American or British. It's probably something like the rule in French that you should not use le weekend, promulgated by l'Académie française — while some people follow it in their writing, many people completely ignore it, even in the most formal writing. Sep 21, 2020 at 14:38

The distinction between definite and indefinite relative clauses is based on whether the speaker assumes the listener already knows which noun the relative clause is modifying (definite) or not (indefinite).

In the sentence "I saw a car which was white," the speaker is introducing a new car into the conversation, and the relative clause "which was white" is providing additional information about that specific car. Since the car is new information to the listener, the relative clause is indefinite.

In the sentence "She went into the apartment, which had blue walls," the speaker assumes that the listener already knows which apartment the subject went into. The relative clause "which had blue walls" is simply providing additional information about the already identified apartment. Therefore, the relative clause is definite.

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