1. Describing a noun directly:
* "We had a fun time at the party."
* "That was a fun movie."
* "She has a fun personality."
2. Used in a comparative or superlative form:
* "This ride is more fun than the last one."
* "That was the most fun I've ever had."
3. As part of a compound adjective:
* "It was a fun-filled day."
* "They had a fun-loving attitude."
Important note: "Fun" is not a traditional adjective in the sense that it doesn't have comparative and superlative forms like "funner" and "funnest." These forms are considered informal and are generally avoided in formal writing.