less commonly, 'in' can serve as an adjective. In this capacity, it often describes a state, condition, or trend.
The striped style is in this season. (Here, 'in' means fashionable or trendy.)
Are you in for the game tonight? (In this context, 'in' means participating or involved.)
as a preposition, 'in' is often used to denote direction, movement, time, and location. It helps establish relationships between nouns and other words in a sentence.
Direction. I ran in the opposite direction.
Movement. She walked in the park.
Time. He arrived in the evening.
Location. The bird is in the tree.
Containment. I put the phone in my pocket.
when 'in' functions as an adverb, it typically describes movement or motion, often indicating the direction or manner of an action.
She ran in to pick up the books. (Here, 'in' describes the direction of her running.)
He drove in quickly. (In this context, 'in' indicates the direction of his driving.)
The dog ran in when he heard the bell. (Here, 'in' provides information about where the dog ran.)