ラジオ英会話 26/3/2(月)L221 What are you doing up?

ラジオ英会話 26/3/2(月)L221 流What are you doing up?
What are you doing up? upの意味は？
This “up” is a very natural, everyday usage.
Meaning of “up” in “What are you doing up?”
In this sentence, “up” means “awake (and not sleeping)”.
So:
What are you doing up?
→ Why are you awake (at this time)?
→ Why aren’t you in bed?

🔍 Nuance
“up” here doesn’t mean “upward.”
It comes from the idea of being up = being out of bed / awake.
🧠 Compare
You should be in bed. Why are you up?
→ もう寝ているはずなのに、なぜ起きているの？
I was up all night.
→ 一晩中起きていた
He stayed up late.
→ 彼は夜更かしした

💡 Summary
up = awake / not sleeping
Often used when someone is awake late at night or very early