A falling out, happening, or coming to pass; hence, that which falls out or happens; occurrence; incident; event.

An occurrence or condition of affairs which brings with it some unlooked-for event; that which incidentally brings to pass an event, without being its efficient cause or sufficient reason; accidental or incidental cause.

An event that is extraordinary, not of the everyday, or a holiday

an event that occurs at a critical time; "at such junctures he always had an impulse to leave"; "it was needed only on special occasions"

a vaguely specified social event; "the party was quite an affair"; "an occasion arranged to honor the president"; "a seemingly endless round of social functions"

the time of a particular event; "on the occasion of his 60th birthday"

an event or series of events, which are closely linked in time