in

/ɪn/ prep (DURING)

Definition

› during part or all of a period of time or an event: We’re going to Arizona in April. What was it like to be a student in 1968? See you in the morning. How many people died in the war? She’s in her forties (= between 40 and 49 years old). › In can also mean no longer than a particular period of time: Can you finish the job in two weeks? › In can also mean at the end of a particular period of time: I should be there in half an hour.

(Definition of in prep (DURING) from the Cambridge Academic Content Dictionary © Cambridge University Press)