It’s rare that I teach an intermediate group and this doesn’t happen:
Miss, what’s the difference between fun and funny?
Fun /ˈfʌn/ is an adjective used to describe something amusing and enjoyable.
Example: “It was a fun holiday. We went to so many different places!”
It can also be used to describe people that you enjoy spending time with.
Example: “She is a fun person to be with. I hope you meet her soon!”
Funny /ˈfʌni/ is an adjective used to describe something that causes laughter.
Example: “He told me a funny joke yesterday and I couldn’t stop laughing.”
So… fun is an adjective?
Traditionally, fun is a noun. But it has become very normal to use it as both an adjective and a noun. The meaning is unchanged and it still refers to something enjoyable and amusing. Be careful with your grammar and make sure you follow the correct rules for nouns and adjectives.
When using fun as an adjective you use it before the noun as in the above examples.
Examples (as a noun):
“Going to the cinema is a lot of fun.”
“I had so much fun at the cinema yesterday.”
Why did you write funny twice in the title?
Funny isn’t always “hahaha”. It can also be used to describe something odd, strange or unusual. Pay attention to context.
“I can’t find my keys. That’s funny, they were here a minute a go.”
“She has a funny way of speaking.”
This can also be used an an adverb. In this case you are describing an action as being odd, strange or unusual.
“He has been acting funny lately. I don’t know what’s wrong with him.”
“She looked at me funny. It made me feel uncomfortable.”
It’s normal to get these words confused so make up your own example sentences to help you remember the different ways they can be used.
Definitions were taken from learnersdictionary.com which is a good resource to get clear English definitions if you’re a learner of English.