Below , Under
The climbers stopped 300 m, below the top of the mountain.
A moment later the sun had disappeared below the horizon.
Measurements : below
The temperature is three degrees below zero.
Parts of Holland are below sea level.
The plane came down below the clouds.
I think the cat is under the bed.
What are you wearing under your sweater?
The whole village is under water.
We usually use under, not below , to mean less than or younger than.
There were under twenty people at the game.
You cann’t see this film if you are under 18.