Occurrence (noun)

1. An event or incident that happens or takes place.
2. The fact or frequency of something happening.
3. Something that exists or is present in a particular place or at a particular time.

Origin:

From occur, from latin occurrere 'run to meet'.

Examples:

1. The occurrence of the earthquake left the city in ruins.
2. The frequency of occurrences of the disease has increased in recent years.
3. The strange occurrence of a red moon has been noted by astronomers.
4. The occurrence of the rare flower is a once-in-a-lifetime experience.
5. The occurrence of a comet passing so close to Earth is a rare event.