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#### plmui

##### Member

Words like 'square/triangle' are easy,
but 'quadrilateral/equilateral(regular) square/equilateral(regular) triangle' are extremely unfamiliar to me.

I haven't heard the word 'quadrilateral' in normal conversations when people describe something's shape.
'The shape of the desk is quadrilateral.'
'Bend the wire into the shape of a quadrilateral.'

I noticed that 'rectangle/quadrilateral' are sometimes translated in just 'square'. (in my country)

And I learned a word 'quadrilateral' today, it makes me curious.

Q. I wonder that if I say something's shape is square, English users will always understand it as a regular quadrilateral?
Or is it not awkward to call quadrilateral/rectangle things just square?

'A license card is square.'(actually rectangle)
'A4 papers are square.'(actually rectangle)
'Excel is full of squares.'(actually rectangle + regular square)

Thank you.

• #### kentix

##### Senior Member
We only use square for things that are square.

We don't use quadrilateral in everyday conversation. We say rectangular. A driver's license is rectangular. A desk is rectangular.

#### plmui

##### Member
We only use square for things that are square.

We don't use quadrilateral in everyday conversation. We say rectangular. A driver's license is rectangular. A desk is rectangular.
Then why it's SpongBob 'Square'Pants?

#### dojibear

##### Senior Member
The words "square" and "rectangle" are very common. I don't know anyone that calls rectangular things that aren't square "square".

The shape of the desk is quadrilateral.
Rectangles are a subset of quadrilaterals (a quadrilateral is any 4-sided figure). So it is more accurate to call that shape a rectangle. When we talk about a shape that is 4-sided but not a rectangle, we usually say "four-sided", not "quadrilateral".

But most native speakers have learned the word. In my high school we took geometry in 10th grade, for an entire school year.

Also "quad" and "lateral" are common English terms, so the word "quadrilateral" is easily understood. It is similar to "trilateral", a fairly common term for "3-sided" that is used in politics.

#### dojibear

##### Senior Member
Then why it's SpongBob 'Square'Pants?
It's a cute name, for a character in a TV show for young children. So it uses words that are easy for young children to say. We do not expect 3-year-olds to know the difference between rectangles and squares.

And "SquarePants" is a catchy name. It has 2 syllables, like SpongeBob. I imagine 2-year-olds can say this. It is much easier to say than "RectangularPants", and much more catchy.

At least his pants are all flat surfaces and right angles (like SpongeBob himself).

#### plmui

##### Member
I don't know anyone that calls rectangular things that aren't square "square".
The SpongeBob was just a joke

So you mean that when I call rectangular things just square, people might feel awkward right?
They certainly distinguish those words and do not use 'square' as the meaning of 4 sided figures.

#### Andygc

##### Senior Member
So you mean that when I call rectangular things just square, people might feel awkward right
Why would people feel awkward if you say square instead of rectangle? They'll just assume you need help with your English.

#### plmui

##### Member
Why would people feel awkward if you say square instead of rectangle? They'll just assume you need help with your English.
OK I got it now.

I know it would be a stupid question for natives,
but non-native speakers may understand why I posted this question. (maybe only Korean)

Basic words about figures that we get to know when learning English at first

There is a really easy word that mean 3 sided figures which is 'triangle',
but there is no easy word that mean 4 sided figures which is 'quadrilateral'.

So who haven't studied math in English have no word that call 4 sided figures,
they tend to say 4 sided figures just square.

quadrilateral with four right angles -> rectangle

Hope you understand why I asked this question
and thank you for the comment!

#### Ponyprof

##### Senior Member
In daily life we say square, rectangle, circle, oval, triangle, and that's it.

The other figures are only for geometry class.

#### Andygc

##### Senior Member
There is a really easy word that mean 3 sided figures which is 'triangle',
but there is no easy word that mean 4 sided figures which is 'quadrilateral'.
Well, actually, no.
There's the word "triangle" which means a shape with three corners, and whose sides are straight. Then there's the easy word "rectangle" which means a shape whose corners are right angles (ie 90°). That also means it has four sides, all of which are straight. A square is, simply, a rectangle whose sides are equal.

While a rectangle is a quadrilateral, there's many a quadrilateral that isn't a rectangle: trapezoid, rhombus, parallelogram and kite.

Edit. Sorry, I have just realised your problem, which perhaps you did not make clear by talking about squares.

If you want to talk about four-sided shapes that are not rectangles, the general term is "quadrilateral". There's no need to have studied anything more than normal school mathematics to know the word, and any educated person should know what you mean. It's just not a word used in everyday conversation.

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#### plmui

##### Member
There's no need to have studied anything more than normal school mathematics to know the word, and any educated person should know what you mean. It's just not a word used in everyday conversation.
I fully agree with you.
But if you've ever learned other languages, you can easily notice that it's bit hard to know scientific/mathematical terms in their language which is even basic.

attraction> Natives will not feel hard to think attraction and repulsion.
covalent bond> All English users who have studied chemistry in school would have heard this word at least once.
But non-natives, except who have studied those subjects in English, may feel hard to understand/know.

Also, the difference between the languages was the factor that had made me confused.
Because, in my language, 'quadrilateral' is the word which is very commonly used in everyday conversations.
Even more than square and rectangle.
'Quadrilateral' is a general term that indicates 4 sided figures, like you said, we use the word 'quadrilateral' very often to call 4 sided figures in daily life like the example sentences I wrote above.

So not knowing the presence of the word 'quadrilateral', I've misunderstood that 'square' plays a role of the meaning of '4 sided figures'

How you've reacted and what you've said were really helpful to me.

#### kentix

##### Senior Member
In everyday life, it is unusual for people to have any need to talk about four-sided figures that aren't squares, rectangles or diamonds. Those are all very common in everyday speech but quadrilateral is not, simply because those other words cover most of everyday experience. And if a word is needed, four-sided is more likely, I think.

Fun fact: when I was learning geometry, our desks were shaped like trapezoids.

Having written the above fun fact, and then looking up the word, I have discovered [who knew?] there are differences in usage between AE/CE and BE.

Trapezoid - Wikipedia

In Euclidean geometry, a convex quadrilateral with at least one pair of parallel sides is referred to as a trapezoid[1][2] (/ˈtræpəzɔɪd/) in American and Canadian English but as a trapezium (/trəˈpiːziəm/) in English outside North America.

The term trapezoid was once defined as a quadrilateral without any parallel sides in Britain and elsewhere. ... However, this particular sense is considered obsolete.

#### Uncle Jack

##### Senior Member
And if a word is needed, four-sided is more likely, I think.

"Triangle"; "four-sided" for anything that isn't a square, a rectangle or a rhombus ("diamond") or possibly a convex kite ("kite"); "five-sided"; "six-sided", and so on.

In answer to the original question, "square" (as an adjective) can also mean at right angles and/or not rounded, so it might be used to refer to a rectangle in contrast to a parallelogram, for example:
A (pointing to a parallelogram): Like this?​
B: No, it needs to be square (meaning it needs to have square corners; in other words, it needs to be rectangular)​

#### Ponyprof

##### Senior Member
I fully agree with you.
But if you've ever learned other languages, you can easily notice that it's bit hard to know scientific/mathematical terms in their language which is even basic.

attraction> Natives will not feel hard to think attraction and repulsion.
covalent bond> All English users who have studied chemistry in school would have heard this word at least once.
But non-natives, except who have studied those subjects in English, may feel hard to understand/know.

Also, the difference between the languages was the factor that had made me confused.
Because, in my language, 'quadrilateral' is the word which is very commonly used in everyday conversations.
Even more than square and rectangle.
'Quadrilateral' is a general term that indicates 4 sided figures, like you said, we use the word 'quadrilateral' very often to call 4 sided figures in daily life like the example sentences I wrote above.

So not knowing the presence of the word 'quadrilateral', I've misunderstood that 'square' plays a role of the meaning of '4 sided figures'

How you've reacted and what you've said were really helpful to me.
Interesting. It sounds like a case where Korean and English have different classification of shapes and a direct translation doesn't work. Always very interesting to find those places in a language.

#### PaulQ

##### Banned
'Quadrilateral' is a general term that indicates 4 sided figures,
For reference:

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#### heypresto

##### Senior Member
If there was such a word, I would call that 'crossed quadrilateral' a hexalateral, or 'two right-angled triangles touching at their right angles'.

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#### heypresto

##### Senior Member
OK. I'll have a go at that over Christmas. It will be more entertaining than the drivel we'll be fed on TV.

#### Uncle Jack

##### Senior Member
For reference:
That first one is a trapezium in BrE, although I have heard that "trapezoid" is a better term. Also, the rhombus looks distinctly like a square to me.

#### kentix

##### Senior Member
Yes, a square is a special rhombus so that's a bad illustration to get that point across.

The only thing I remember calling a trapezoid when I learned geometry in junior high school was what they call an isoceles trapezoid. Either I remember wrongly or we weren't given the whole picture.

#### JulianStuart

##### Senior Member
Indeed. A rhombus is an equilateral parallelogram There is also a "quadrangle" although it seems to be used mainly for architectural reference these days.

#### plmui

##### Member
have different classification of shapes
The classification of shapes is same. Because it's math!
What 'quadrilateral' in Korean indicates is same with what 'quadrilateral' in English means.
But the difference is whether the term 'quadrilateral' is used as an everyday word or not.

In everyday life, it is unusual for people to have any need to talk about four-sided figures that aren't squares, rectangles or diamonds.
Because of the reason like above, in my language, it's usually used as the word which indicates squares or rectangles or diamonds in everyday conversations.
And it was the difference that made me confused.

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#### PaulQ

##### Banned
OK, in response to public demand, I have amended the picture above.
But the difference is whether the term 'quadrilateral' is used as an everyday word or not.
Only by mathematicians and the like or if the speaker is being very specific.

Of the figures above, only 4 - "square" would be used in everyday language; of the rest, they would be described by phrases (and hand gestures giving 'air-drawings'.) As examples - there'll be lots of other ways to describe them -
1 - (Either a lengthy description, or draw it.)
2 -"It's square [but wider than it is tall/long]"
3 - "It's square, but the top is [a lot/bit] shorter than the bottom"
5 - "It's a diamond / "diamond shaped"
6 - "It's square, but wider than it is tall/long, and it's slanting to the side
7 - "It's shaped like a kite"
8 - "It's got four sides but none are the same length.
9 - "It's like an arrowhead with one corner poked into the V
10 - (Either a lengthy description, or draw it.)

#### Edinburgher

##### Senior Member
It sounds like a case where Korean and English have different classification of shapes and a direct translation doesn't work. Always very interesting to find those places in a language.
It seems that German is similar to Korean in this respect: The German generic word for a quadrilateral is commonly used in everyday language.
To be more precise, notice that the literal meaning of "quadrilateral" is a figure with four sides. Thus it is not in the same classification method as triangle, because we don't call it a trilateral. English does of course also have the word quadrangle, and it is the equivalent of this that German uses for a shape with four corners. Germans are therefore not at all unlikely to call a rectangle a "four-corner" (which is also the word used to describe the most general form of quadrilateral), even though the word "right-corner" for a rectangle also exists in common use.

#### Packard

##### Senior Member
If there was such a word, I would call that 'crossed quadrilateral' a hexalateral, or 'two right-angled triangles touching at their right angles'.
I guess it is named for the number of lines required to construct the shape. In this case it took just four lines.

But geometric shape names don't always appear in language. We say "triangle" for all types of triangles. We specify "right angle triangle" and "equilateral triangle" if it is important to understanding the image.

I never hear "oblate spheroid" in normal language. I do hear "He threw the football", but never "He threw the oblate spheroid".

In general we use terms that will be most easily understood by our audience. If our audience consists of engineers and mathematicians then any geometric term is fine. But if it is a more general audience we need to use terms that will be readily understood by that general audience even if it sounds like we are "talking down" to the engineers and mathematicians.

#### plmui

##### Member
English does of course also have the word quadrangle, and it is the equivalent of this that German uses for a shape with four corners.
I think German also name the basic figures by the number of their corners.
Dreieck> 3 corners
Viereck> 4 corners
Fünfeck > 5 corners
Sechseck > 6 corners

But English goes like triangle - quadrilateral - pentagon - hexagon,
not triangle - quadrangle - pentangle - hexangle. (maybe -agon=angle, I think)

So without knowing the word 'quadrilateral', I had been misunderstanding it was
triangle - square - pentagon -hexagon.

I thought
a figure with 4 sides = square
a figure with 4 equal sides and 4 equal angles = regular square.

#### Packard

##### Senior Member
[...]

I thought
a figure with 4 sides = square
a figure with 4 equal sides and 4 equal angles = regular square.
In American English

a figure with four sides = rectangle
a figure with four equal sides = square

#### kentix

##### Senior Member
I thought
a figure with 4 sides = square
a figure with 4 equal sides and 4 equal angles = regular square.
Your post makes more sense now. Square, far from being a general term, is a reference only to a very specific and special four-sided figure.

In order of increasing "specialness":

Any length sides, any angles > four equal angles, no restriction on sides (except caused by the angles) > for equal angles, four equal sides

I suppose you could call a square a "regular rectangle" but I don't know if anyone ever does.

#### Packard

##### Senior Member
Your post makes more sense now. Square, far from being a general term, is a reference only to a very specific and special four-sided figure.

In order of increasing "specialness":

Any length sides, any angles > four equal angles, no restriction on sides (except caused by the angles) > for equal angles, four equal sides

I guess "parallelogram" fits in that list somewhere. I'm not sure exactly where to fit it. Probably between quadrilateral and rectangle.

#### kentix

##### Senior Member
It's sort of a separate branch. To get a general parallelogram you have to specify the sides first, before the angles.

If you specify a paralellogram with equal sides then you get a rhombus.

If you give that rhombus equal angles then you're back to a square again.

#### Packard

##### Senior Member
It's sort of a separate branch. To get a general parallelogram you have to specify the sides first, before the angles.

If you specify a paralellogram with equal sides then you get a rhombus.

If you give that rhombus equal angles then you're back to a square again.
But squares and rectangles are just parallelograms with 90° angles.

#### kentix

##### Senior Member
Yes, they are all interconnected. It just depends on how you want to look at it.

#### Edinburgher

##### Senior Member
I think German also name the basic figures by the number of their corners.
Indeed. That's the gist of what I said, but I did so while carefully avoiding quoting the actual German words, because it is against the rules of the English-Only forum.

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