A favorable opportunity; a convenient or timely chance.

“At this point, she seized the occasion to make her own observation.”

The time when something happens.

“on this occasion, I'm going to decline your offer, but next time I might agree.”

An occurrence or state of affairs which causes some event or reaction; a motive or reason.

“I had no occasion to feel offended, however.”

To cause; to produce; to induce

“it is seen that the mental changes are occasioned by a change of polarity”