Sit-up and Stay up

Sit-up noun - A stomach exercise in which a person sits up from a supine position without using the arms for leverage.

Stay up and sit-up are semantically related. In some cases you can use "Stay up" instead a verb phrase "Sit-up".

Stay up verb - Not go to bed.

Sit-up and stay up are semantically related. Sometimes you can replace phrase "Sit-up" with "Stay up", this terms are similar.