Fun (noun)

1. Enjoyment, amusement, or lighthearted pleasure.
2. A source of enjoyment or amusement.
3. An amusing or entertaining event or experience.
4. A playful or mischievous act.
5. A state of being cheerful and lively.

Origin:

Late 18th century (originally funfair): abbreviation of funfair, or from an alteration of dialect fawn, from old english fagnian 'to rejoice'.

Examples:

1. We had a lot of fun at the party.
2. She is always looking for fun.
3. The theme park was full of fun and excitement.
4. He had a fun idea for the prank.
5. The concert was a fun and energetic performance.