うちに vs 間に — both mean 'while', what's the actual difference?

Question

I keep mixing these up. My textbook example was 子供が寝ているうちに掃除をした (cleaned while the kid was sleeping) but I've also seen 間に used the same way. Is うちに more about 'before the window closes' and 間に just neutral duration?

Accepted Answer

Good instinct. うちに carries a nuance of 'before this temporary state ends, so act now' — often implying the result wouldn't be possible or as easy afterward (若いうちに勉強しろ = study while you're young, i.e. before that's gone). 間に is more neutral, just 'during the interval of X'. They overlap a lot in casual speech but うちに is the one you'll see in advice/warnings.

Answer

The 'before it's too late' feeling is the part that finally made it click for me too. 忘れないうちにメモしておく = write it down before you forget, not just 'during not-forgetting'.