You know, the little plastic, metal or wooden circles that go through a hole on the other side of the shirt. In the UK they’re buttons, but I know that, in the US and (I think) Canada, buttons are little metal safety-pinned circles with logos or slogans on, that we in the UK call badges.
Of course, perhaps the word safety-pin is one of those two-countries-divided-by-the-same-language words too. :dubious:
Um, they’re buttons. Your badges are also called buttons, but that’s a pretty minor use of the word.
We call them both buttons. Badges are the shiny things policemen have. Or Boy Scouts.
Buttons? Since when? Where I grew up in Michigan we always called them circular ring retainers. Sure, it was awkward when your button-fly jeans (why do the call them that anyway?) were circular ring unretained, and someone had to remind you to “circularly ring retain your jeans!” We should have invented better words.
Question asked and answered, thanks. 
I don’t think it was a stupid question, though - why would I know that you use the same word for two completely different items? There are enough differences in Brit-US terms, after all, especially when it comes to clothing.
You wouldn’t, necessarily - I think people were just reacting (in a good natured way) to what appeared to be the notion that a single word couldn’t possibly have more than one meaning (I don’t think you thought that - it just looked a bit like it).
For fun, consider the many meanings of pudding, in British English.
The origin of the double usage stems from the Great Depression. Nobody could afford belts, and it was common for folks to use Herbert Hoover “A chicken in every pot” campaign buttons to hold their pants up during the Rope Shortages.
I’ve heard them called stays. Is that just me?
Oh, I’m not angry, annoyed, irritated or even discombobulated, no worries. I know that single words can have more than one meaning, but had no way of knowing if that applied to this word - except for asking on here. I don’t think it’s a piss-take worthy question.
Oops, my bad. I thought you were talking about…er, something else. Sorry, disregard!
I question whether they are completely different - both are disk-like objects that (commonly) lie parallel to and just above an item of clothing.
The thing you push in an elevator to select your destination floor goes by the same name, but is often substantially different to these two.
There are no stupid questions, only stupid people.
Now, what do Americans call “American Cheese”?
Gross. 
We call it American Cheese, too.
Edit: Apparently what Americans/Canadians call Swiss Cheese isn’t called Swiss Cheese in Switzerland… :o
On the topic of item of clothing: I understand that “pants” in British English can mean “female underwear”. Is it ever used in the UK to mean “trousers” in the North American sense, or is that its only meaning?
There are many varieties of tasty Swiss cheese. One, which has a lot of holes in it, is called Emmentaler.
To be clear, by the way, in the US a “badge” can be either a cloth emblem sewn onto a garment (such as those worn by Boy Scouts), or the metal token that a police officer uses to identify himself as police.
You can make the same argument with respect to British English. Brits have two sense for the word “badge.” It can mean both the shiny metallic things used as insignia by policemen and such, but it can also mean the round metallic things with words on them used by other people.
In fact, this is true of a number of cases where British and American English differ. (Indeed, it’s true of a lot of cases where dialects of various languages differ.) There will be three meanings, which we will call A, B, and C. There will be two words, which we will call X and Y. British English will use word X for the meanings A and B and will use word Y for the meaning C. American English will use word X for the meaning A and will use word Y for the meaning B and C. It’s just as true in such cases that British English is using one word for two meanings as it is the American English is using one word for two meanings.
I call 'em “fingers”. 
For real fun have an American and a Brit define potato “chips”.
Americans call “badges” either buttons or pins. Both of those words have other meanings, of course, but either can be used to describe the little round thing with the name of your favorite band on them.