In, into

We use in to talk about where something is in relation to a larger area around it:

A:

Where’s Jane?

B:

She’s in the garden.

I’ve left my keys in the car.

We use into to talk about the movement of something, usually with a verb that expresses movement (e.g. go, come). It shows where something is or was going:

A:

Where’s Jane?

B:

She’s gone into the house.

Helen came into the room.

With some verbs (e.g. put, fall, jump, dive) we can use either in or into with no difference in meaning:

Can you put the milk in/into the fridge?

Her keys fell in/into the canal.

We use be into to express enthusiasm or strong interest for something:

He’s really into his work.

I’m into classical music and Thai food.

We use into after verbs describing change:

We’ve translated the course into six different languages.

She changed into her swimming costume and went for a swim.

They divided the cake into four pieces.

Not: They divided the cake in four pieces.

We use in to make a number of phrasal verbs:

I was feeling very tired and I couldn’t really take in what she was saying. (understand)

Please call in and see us next time you’re in the area. (visit us briefly)

A good learner’s dictionary will include the most common phrasal verbs with in.