The word "in" can be used as a preposition, an adjective, or as an adverb. It has many interesting applications, but generally we use the word "in" to show that a person or a thing is inside, within, included, a part, or available.
…in his glove
The ball is in his glove. (preposition)
The passengers are in the plane. (preposition)
Their flight is in. (adjective)
They flew in from New York. (adverb)
You can use "in" when something arrives or is present:
When will they be in? (When will they arrive?)
The doctor isn’t in right now. He’ll be in later. (He isn’t present. He isn’t there.)
A large shipment of furniture is in.
Are you going to be in tomorrow? (in = at work)
What time will you be in?
You can use "in" with many different verbs to form idioms. Some idioms are hard to understand, but these examples might help:
Come in.Hi. Welcome to my home. Come in.
Go in.Cathy has to go in for a check up tomorrow.
Move in.We found a new apartment. Next week we’re going to move in.
Drive in. Gordon drove all the way in from Alaska.
Eat in.Do you want to eat out tonight or eat in?
Weigh in. The boxers needed to weigh in before their fight.
Walk in.Tracy doesn’t have an appointment to get her hair cut. She’s just going to walk in.
Run in.I need to run in and get something in my house. Will you wait here?
Fly in. Denise flew in this morning from Houston.
Turn in.The office manager told Juanita to turn in her keys after she was fired.
Hand in. The teacher asked the students to hand in their assignments.
Step in. The police should step in before this situation gets out of control.
Sit in. I’d like to see what you are teaching today. Do you mind if I sit in?
Sleep in. Bruce sleeps in until about noon on Saturday because he doesn’t have to go to school.
Check in. When we arrive at the hotel, we’ll need to check in.
Stop in. Next time you’re in Chicago, you should stop in for a visit.
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