happen
verb
ˈhæpən 
ˈhæpən 
1 [intransitive] to take place, especially without being plannedYou'll never guess what's happened!Accidents like this happen all the time.Let's see what happens next week.I'll be there whatever happens.Is this really happening or is it a dream?I don't know how this happened.2 [intransitive] to take place as the result of somethingShe pressed the button but nothing happened.What happens if nobody comes to the party?Just plug it in and see what happens.3 linking verb to do or be something by chancehappen to be/do something She happened to be out when we called.You don't happen to know his name, do you?This happens to be my favourite restaurant.The door happened to be unlocked.it happens that… It happened that she was out when we called.4 [transitive] happen to be/do something used to tell somebody something, especially when you are disagreeing with them or annoyed by what they have saidThat happens to be my mother you're talking about!Idioms
anything can/might happen
used to say that it is not possible to know what the result of something will be
as it happens/happened
used when you say something that is surprising, or something connected with what somebody else has just said
I agree with you, as it happens.As it happens, I have a spare set of keys in my office.it (just) so happens that…
by chance
It just so happened they'd been invited too.these things happen
used to tell somebody not to worry about something they have done
‘Sorry—I've spilt some wine.’ ‘Never mind. These things happen.’Phrasal verbs
happen on something
(old-fashioned) to find something by chance