Which of these does not form part of a three-piece suit?

JoeK, Perhaps American English, not British English?

nonsense question uk us very different, if you don't know the difference, don't ask the question

JoeK, the first sentence says trousers not pants and that the waistcoat is called a vest in North America. Are we reading different questions?

2 things wrong. it's not a vest it's a waistcoat. they are not pants, they're trousers.