a very large building that is capable of protecting someone or something, such as a king
The castle is old.

the white object that circles the Earth and can be seen in the night sky; an object similar to the moon that circles another PLANET
One day we will live on the moon.

a large body of salt water that covers most of the surface of the earth
I think it’s too cold to swim in ocean.

to travel across water in a boat or a ship
We should go sailing at the lake this weekend.

to live somewhere for a short amount of time
I will stay with family until the term begins.

to go somewhere for a short period of time
Soon, I’m going to visit Rio for the first time!