Occasion (noun)

1. An event or time that is suitable or appropriate for a particular thing to happen.
2. A particular event or situation that is worth noticing.

Origin:

Middle english, from old french occasion, from latin occasion-, occasio opportunity, from occidere to fall.

Examples:

1. This is a special occasion.
2. I will wear my best dress on the occasion.
3. He took the occasion to speak his mind.
4. On the occasion of her birthday, he gave her a gift.
5. The concert provided an occasion for us to get together.