Overnight vs. Over Night: Which Is Correct? - The Blue Book . . . Let’s start by clearing up any confusion: overnight is the correct spelling so long as you mean to describe something that took place “all through the night ” In most cases, over night (two words) would be incorrect and possibly considered a typo
OVERNIGHT | English meaning - Cambridge Dictionary You can stay overnight if you want to Don't forget to pack an overnight bag (= a bag for things that you need when you stay away from home for a night)
OVERNIGHT definition and meaning | Collins English Dictionary If something happens overnight, it happens throughout the night or at some point during the night The weather remained calm overnight The decision was reached overnight Overnight is also an adjective