In and inside are the same in many cases. You can say:
▶️ We are in the house.
= We are inside the house.
▶️ The clothes are in the closet.
= The clothes are inside the closet.
The word inside implies that the thing is physically enclosed – it is in a container (a
box, a vehicle, a building with walls, etc.)
This means that when talking about location, time, being included, or other
situations where you are not physically surrounded, you should use in, not inside:
▶️ I live in Australia.
▶️ My birthday is in July.
▶️ He plays guitar in a band.
The word into implies movement or transformation:
▶️ She jumped into the swimming pool.
▶️ We went into the house.
▶️ The car crashed into a telephone pole.
▶️ The caterpillar turned into a butterfly.
With the verbs put, throw, drop, and fall, you can use either into or in:
▶️ He put the card into/in his pocket.
▶️ I threw the paper cup into/in the trash.
▶️ She lost her balance and fell into/in the river.
The word within means “inside the limits” – and in this case the limits are non-
physical. They can be limits of time or distance, or an area of understanding:
▶️ The results will be delivered within fourteen days.
▶️ Most car accidents occur within five miles of home.
We also have some expressions using within:
▶️ within earshot = at a distance where you are able to hear something (such as
a conversation)
▶️ within reason = to the degree that good judgment would allow
▶️ within reach / within one’s grasp = able to be taken with your hand, or able
to be accomplished
You can also use within to describe a person’s inner feelings (in this case, you can
also use “inside”):
▶️ He tried to hide the anger burning within/inside him.