v. 25B6; verb
the accident occurred at about 3.30 : HAPPEN, take place, come about, transpire, materialize, arise, crop up; N. Amer. informal go down; poetic/literary come to pass, befall, betide; archaic hap; formal eventuate.
the disease occurs chiefly in tropical climates : BE FOUND, be present, exist, appear, prevail, present itself, manifest itself, turn up.
an idea occurred to her : ENTER ONE'S HEAD/MIND, cross one's mind, come to mind, spring to mind, strike one, hit one, dawn on one, suggest itself.