n.
   - a particular event, or the time at which it takes place. ▸a suitable or opportune time. 
- a special event or celebration.
- formal reason; cause:![]()  we have occasion to rejoice. 
v.
 formal cause.
Phrase
  
    - on occasion
 from time to time.
- rise to the occasion
 perform well in response to a special situation.
- take occasion
 make use of an opportunity to do something.
 
  Etymology
  ME: from L. occasio(n-) ‘juncture, reason’, from occidere ‘go down, set’.