inside
used as a preposition
When someone or something is in a building, vehicle, or container, you can say that they are inside it.
They heard loud music coming from inside the building.
Jaya wondered what was inside the box.
Be careful
Don't say that someone or something is ‘inside of’ something.
Don't say that someone or something is ‘inside of’ something.
used as an adverb
Inside can also be an adverb.
Marta opened the door and invited him inside.
He gave me a package with something soft inside.