chance

noun:a possibility or probability of something happening
- There's a good chance it will rain tomorrow.
noun:an opportunity to do or achieve something
- She was given a chance to prove her skills.
noun:the occurrence of events in the absence of any obvious intention or cause; luck
- We met by pure chance at the airport.
verb:to do something without planning or intention
- I chanced upon an old friend in the city.
verb:to risk something
- He decided not to chance driving on the icy roads.
adjective:accidental or unplanned
- Our chance encounter led to a long friendship.