If you mean annual event, it occurs yearly.
An event of some sort that happens twice a year.
Yes. Example: Washington Annual Luncheon Event
Yes, the name of an annual luncheon event should be capitalized.
An annual event occurs once a year.
If an event keeps on occurring that means the event is at least annual. If it occurs more than once a year that makes the event perennial or biannual if it only occurs twice.
Annual event
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The Super Bowl is an annual event because it occurs once a year, at the end of each NFL season.
An anniversaryanniversary: the annual celebration of an event on that day of a previous year
something annual at gamestop.
Something that happens once a year.