British, American & Australian, American

the correct way to behave in a particular social situation.

Wearing jeans in an office environment isn't really the done thing. (usually negative)

You can't smoke during the meal. It's not the thing to do.

• there's no law against doing something
• there's no law against something
• There's no peace for the wicked!
• There's no rest for the wicked!
• There's no smoke without fire.
• There's no such thing as a free lunch.
• there's no telling
• there's nothing to it
• There's nothing to it.
• There's no time like the present.
• There's no time to lose.
• There's no two ways about it.
• There's one born every minute.
• There's one for the books.
• There's safety in numbers.
• there's the rub
• There's the rub.
• the rest is history
• there's ... to be said for
• there's ... to be said for doing something
• there's ... to be said for something
• There, there.
• There wasn't a dry eye in the house.
• the road to hell is paved with good intentions.
• the roof caves in