Ok so... My friend and i used to walked to school sometimes but we haven't done that recently. I messaged him " we haven't walked in a while " He replied " for a while* " And now we're arguing over it. Which is correct? Thanks
I've heard both, but I believe "in a while" is more commonly used in this case.
"... in a while" would be used more for things that are not actively occurring, to denote the time since it last happened or until it will happen again.
"... for a while" would indicate how long something happened or has been happening.
Think of how "a little while" would be used in the same example. "I will walk in a little while" would mean that I'm not walking now, but will relatively soon. "I will walk for a little while" would mean that I'll start walking (probably soon) but I won't walk for a long amount of time.