English for Today by Ganiu Abisoye (Dr GAB)
IN FUN or FOR FUN?
If you do something in fun, you do it as a joke or for amusement, without intending to cause any harm:
You should avoid such statements, even for fun. ✖️
You should avoid such statements, even in fun. ✔️
If you do something for fun or for the fun of it, you do it in order to enjoy yourself rather than because it is important or necessary:
I think he wants a PhD just in fun. ✖️
I think he wants a PhD for fun. ✔️
I think he wants a PhD for the fun of it. ✔️
GAB