occasion

Etymology

Borrowed from Middle French occasion, from Old French occasiun, from Latin occasiōnem, noun of action from perfect passive participle occasus, from verb occido, from prefix ob- (“down", "away”) + verb cado (“fall”).

noun

1. A favorable opportunity; a convenient or timely chance.
   At this point, she seized the occasion to make her own observation.
   I'll take the occasion which he gives to bring / Him to his death. 1690, Edmund Waller, The Maids Tragedy Alter'd
2. The time when something happens.
   on this occasion, I'm going to decline your offer, but next time I might agree.
3. An occurrence or state of affairs which causes some event or reaction; a motive or reason.
   I had no occasion to feel offended, however.
4. Something which causes something else; a cause.
   it were too vile to say, and scarce to be beleeved, what we endured: but the occasion was our owne, for want of providence, industrie and government …. 1624, John Smith, Generall Historie, Kupperman, published 1988, page 130
5. (obsolete) An occurrence or incident.
6. A particular happening; an instance or time when something occurred.
   I could think of two separate occasions when she had deliberately lied to me.
   a momentous occasion in the history of South Africa
   In the last two decades, North Korea has on various occasions conducted highly provocative missile and nuclear tests and promised to turn Seoul into a sea of fire. April 9, 2013, Andrei Lankov, “Stay Cool. Call North Korea’s Bluff.”, in New York Times
7. Need; requirement, necessity.
   I have no occasion for firearms.
8. A special event or function.
   Having people round for dinner was always quite an occasion at our house.
9. A reason or excuse; a motive; a persuasion.

verb

1. (transitive) To cause; to produce; to induce
   it is seen that the mental changes are occasioned by a change of polarity
   […] although overcrowding on the trains running via London Bridge has occasioned considerable discomfort to regular travellers, it was noticed that the alternative route was not extensively patronised, and that the trains were seldom more than half-filled. 1946 November and December, “Additional London-Dartford Services”, in Railway Magazine, page 386