Men likely have a closet full of these and women definitely have a few, too — even if they don't exactly know what to call them.
You probably refer to that shirt with a collar and buttons along the middle as a "button-up," and you wouldn't be wrong, but is it also a "button-down?" That's what Chrissy Teigen would like to find out, at least according to one of her tweets from Sunday.
Her Twitter poll received a frenzy of replies with people sounding off on their opinions and while their doesn't seem to be a consensus from the tweet, TODAY Style is going to break it down for you.
The main thing to know? Button-down shirts have extra buttons so you can fasten the collar and keep it in place. Take a look at "Modern Family" star Ty Burrell's collar here.
"A button-down is a button-up, but a button-up isn't necessarily a button-down," style expert Megan Collins of Style Girlfriend, a website for men's fashion, explained. "In the way that an apple is a fruit, but not all fruits are apples."
Here's a tip to help you remember: You can button down the collar on a button-down.
Not all button-up shirts have those extra buttons, though. See actor Alexander Skarsgard as an example.
The reason behind button-downs is rooted in function. The shirt was created for polo players in England to keep their collars in place while they rode horses, Collins explains. The style stuck and today it's considered a slightly more casual version of a dress shirt.
Funny enough, what's commonly known today as polo shirts — think Ralph Lauren — don't actually have those extra buttons. Those were made for the tennis court, not the polo field, Collins says, where there's "not as much bopping up and down" as there would be on a horse.
So there you have it, Chrissy Teigen! Hopefully, TODAY Style has solved this great debate for you once and for all.
This article was originally published on July 25, 2016 on TODAY.com.