Ok, if I say "Her face is triangle*".

I believe that the sentence is wrong logically because "triangle" is never an adjective but a noun. The face is a face and thus can not be a shape, right?

I think it is ok to say "Her face shape is a triangle*" because "triangle is a shape". A face shape is a shape, so that sentence is OK.

But if we say "Her face is square*", then that is OK because "square" is an adjective with the meaning "having a square shape".

I don't understand why we have "Square" (noun) & "Square" (adj), but "Triangle" (noun) but no "Triangle" (adj).

However, Google returns with 440 results for "Her face is triangle".

And saying "Her face is triangular" is OK right?

I ask this question because I am not sure whether I am correct.

  • 1
    I think this is more idiomatic: She has a triangle-shaped face. By the same token, these should be acceptable, too: Her face is triangle-shaped. Her face is triangular-shaped. – Damkerng T. Dec 15 '15 at 9:26
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    RE: I believe that the sentence is wrong logically because "triangle" is never an adjective but a noun. I agree that triangular would be a better choice. That said, be careful about using words like never when it comes to English. Moreover, be careful about Google hit counts, too. If you page through those 400+ results, you'll find it's more like 20 than 400 – and, furthermore, most of those are saying "Her face is triangle-shaped", which is quite different from "Her face is triangle." And one hit has VERY poor English: My familliy is 5 people. At first, I discribe about my mother. – J.R. Dec 15 '15 at 10:23
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    @DamkerngT. - "Triangular-shaped" sounds odd, because "triangular" is already describing a shape. Just "Her face is triangular" sounds a little more fluent. – stangdon Dec 15 '15 at 12:45
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    As a note: you can't say "her face shape is triangle", it would have to be "her face shape is a triangle". – AndyT Dec 15 '15 at 15:15
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    You could say Her face is a triangle. As a singular count noun, triangle normally needs a determiner before it. – user20792 Dec 15 '15 at 19:31

The adjective form of various shapes ending in "angle" is usually shapename-ular.

So, for example.

circle -> circular
rectangle -> rectangular
triangle -> triangular

Square is an exception. The adjective form of square is just square.

The correct form of what you're trying to say is

Her face is triangular.

Though I don't think someone would take kindly to that comment, so I would keep that comment in your exercise books only.


This is a case in English where idiomatic syntax prevails over rules of grammar in practical usage.

Most native speakers would say one of the following (most common at the top):


  • Her face is shaped like a triangle.
  • Her face is triangular.
  • Her face is triangularly shaped.
  • Her face is shaped triangularly.
  • Her face is shaped triangular. (This one is incorrect grammar because triangular is an adjective, not an adverb. But it is still used; albeit incorrectly.)


  • Her face is shaped like a square.
  • Her face is squarely shaped.
  • Her face is square-shaped.
  • Her face is shaped squarely.

Source: Native speaker

  • As another native speaker, "Her face is shaped like a triangle" sounds more like an insult or a joke. "Her face is triangular" or "She has a triangular face" would seem more polite. – Dave Dec 15 '15 at 18:19
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    I would sooner say "triangle-shaped" than "triangularly-shaped". Adding -ly to "[shape]ular" to form an adverb would likely be understood, but in my experience is only found in practice when someone speaking is fumbling with their words. – talrnu Dec 15 '15 at 18:20

You've gotten an answer to the part about "Her face is triangle/ular", so let me address another of your sentences:

*Her face shape is triangle.

This sentence is also incorrect. Native speakers would never say her face shape. We would instead say the shape of her face. And we would still use triangular instead of triangle with this subject phrase.

(This is Just One Of Those Things. I cannot think of an explanation.)


Seconding triangular - "square" is not a very important exception because it is just a special case of rectangular.

So the rule to add -ular certainly holds.

See also polygonal.

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