Meaning of "happen" in Essential American English Dictionary

happen

verb us /ˈhæp·ən/

A2 If an event or situation happens, it exists or starts to be done:

Accidents can happen to anyone.
We can’t let a mistake like this happen again.
Did you hear what happened to Jamie last night?

A2 to be the result of an action, situation, or event that someone or something experiences:

What happens if we miss the flight?

(Definition of “happen” from the Webster's Essential Mini Dictionary © Cambridge University Press)