Other forms: occurred; occurs; occurring
Use the verb occur when an event or a thought happens, like when it occurs to you that you've left home without your umbrella. Maybe you didn't hear the forecast that showers would occur this afternoon.
The verb occur comes from the Latin, occurrere, “to meet” or “to present itself.” When something occurs, it comes into being, like a thought that seems to present itself from out of the blue, like when it suddenly occurs to you that you forgot to ask your guests if they'd like a cup of tea, or that it would never occur to your Mother that some people spend a small fortune on handbags. Events can also occur, meaning "take place," like a meeting that will occur tomorrow.