Lapels are the folded flaps of cloth on the front of a jacket or coat and are most commonly found on formal clothing and suit jackets. Usually they are formed by folding over the front edges of the jacket or coat and sewing them to the collar, an extra piece of fabric around the back of the neck.

What is the purpose of a lapel?

Why Lapels Exist

However, when the weather would get hot, wearers would be unfasten those stuffy high collars and leave them flopped to the sides, to ensure maximum air flow and cooling. Over time, that more relaxed look evolved into what we know as the lapel today.

Should a vest have a lapel?

Vests with lapels are not technically wrong, but a vest without lapels would be my preference. Lapels on a vest look dressier and feel bulkier, and since a suit with a vest is already a killer look, there's no need to over-egg it.