I would consider the word common knowledge, if only because it's used in both nature documentaries and my elementary/middle school natural sciences classes.Word that means active during the day.
There's a person I know here in Taiwan who knows it, and I'm impressed they know it, and they're confused because they figure it should be fairly common knowledge. I, however, only ever learned "nocturnal" in school, and learned its opposite when I was much older and during my own independent reading. So I'm trying to determine exactly how impressed I should be.