happen (to take place, usually without being planned): An eclipse happens when the sun, earth, and moon are in a straight line.
occur formal (to happen, especially unexpectedly): These problems occur in all families.
take place (to happen, usually events that have been arranged or planned): The wedding will take place in November.
arise (to happen, especially a problem or a difficult situation): We do our best to deal with the problems as soon as they arise.
come about phrasal verb (to take place, especially by chance): How did this problem come about?
come up (to occur or present itself): Opportunities like this don’t come up every day.
crop up (to appear or happen unexpectedly): In our office, new problems crop up every day.
materialize usually used in negative statements (to happen or become real): The pay raise they promised us has so far failed to materialize.
