From the Merriam-Webster dictionary

The scarf is a perfect complement to her outfit.

This pattern is easy to understand, A is complement to B

From the Collins dictionary

The green wallpaper is the perfect complement to the old pine of the dresser.

Again, the same pattern A is complement to B.

To make it easier to understand, could I say "B was missing something, A could help"?

The completeness is more about beauty, in particular, some kind of addition to existing beauty.

However, that kind of completeness is probably difficult for someone, like me, to understand. I'd never managed to distinguish my wife's scarves. So, I can't even make up what B is missing in any of those examples!

Besides, beauty is somehow a matter of opinion. Are there some other situations where the complement is easier to measure?

For example, could I call my headset a complement to my laptop, which can let me hear whatever I want to listen to without disturbing anyone else?

From the Cambridge Dictionary

We had a full complement of reporters and photographers along.

This example doesn't use the pattern A is complement to B, which makes it difficult to say B is missing what.

  • A complement does not supply something "missing", it supplies something extra. Commented Jun 19, 2020 at 10:59
  • 1
    There are several distinct meanings for complement (and although it looks similar to the word 'complete' is different). Lexico's meaning 1 is about your scarf example. Meaning 2 is about the reporters. In the scarf example, there was nothing missing, and in your headphones example below, they don't complement the laptop, they are an extra. Commented Jun 19, 2020 at 11:38
  • ... and in the answer, that is a distinct mathematical term. Commented Jun 19, 2020 at 11:43

1 Answer 1


Let A be an angle in mathematics (specifically an acute angle, that is, between 0 and 90 degrees). The complement of A is the angle which fills up the rest of the gap so as to make 90 degrees together with A.

So if angle B is the complement to angle A, then A + B = 90 degrees.

  • Thank you. Your answer is so clear. Thanks a lot! How about my example of laptop? Are there any other daily life examples for it?
    – RobertH
    Commented Jun 19, 2020 at 10:58
  • You could do, if you so wished, but it's the sort of language I'd only really expect to hear in an advertisement. As for the quote from the Cambridge dictionary, "a full complement" means "all the reporters needed to make the party complete." The word "complement" itself means "complete-ment", that is, what you need to "complete" something. As such it's usually flowery and pretentious language, although "a full complement" is a common cliche. Commented Jun 19, 2020 at 11:01
  • Thank you. So, calling headset a complement to laptop sounds like an advertisement, right? How could I make it not sound like that?
    – RobertH
    Commented Jun 19, 2020 at 11:22
  • 1
    @RobertH I don't know, I'm not writing your essay. I'd just say that the headphones are a useful accessory or adjunct, unless you really are singing the praises of your system to someone you're trying to persuade that yes, indeed, you do have just the best of toys. Commented Jun 19, 2020 at 11:25

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