1To put, insert, or bring something into a container, machine, or place — a broad, everyday sense of "putting something in."
荷物をスーツケースに入れる。
Put the luggage into the suitcase.
砂糖をコップに入れてよく混ぜる。
Put sugar into the cup and mix well.
スマホに新しいアプリを入れた。
I installed a new app on my phone.
指輪に誕生石を入れてもらった。
I had a birthstone set into the ring.
2To admit or accept a person into a group or organization; to hire or bring someone on as a member.
今年は新入社員を五人入れる予定だ。
We plan to hire five new employees this year.
サークルに後輩を一人入れることにした。
We decided to bring one underclassman into the club.
彼の実力を見て、チームに入れることにした。
Seeing his skill, we decided to bring him onto the team.
3To accept or grant a request, demand, or opinion — often written 容れる specifically in this sense of "taking someone's input to heart."
会社は組合の要求を一部容れた。
The company accepted part of the union's demands.
彼は人の意見を素直に容れる性格だ。
He's the type who readily takes other people's opinions to heart.
4To include something within a range, group, or count.
税を入れると合計で三千円になる。
Including tax, the total comes to 3,000 yen.
このリストに私の名前も入れてください。
Please include my name on this list too.
5To pay (rent, fees, etc.), commonly in the set phrase 家賃を入れる ("to pay the rent").
毎月末に家賃を入れることになっている。
I'm supposed to pay the rent at the end of every month.
6To cast a vote, as in 一票を入れる ("to cast one's vote").
日曜日の選挙で一票を入れてきた。
I went and cast my vote in Sunday's election.
7To make or brew tea, coffee, etc., as in お茶を入れる ("to make tea").
お客さんが来たので、お茶を入れた。
A guest came over, so I made some tea.
毎朝コーヒーを入れてから仕事を始める。
I make coffee every morning before starting work.
8To turn on or switch on a device or machine.
暑いのでエアコンを入れた。
It was hot, so I turned on the AC.
スイッチを入れると画面が明るくなった。
When I flipped the switch, the screen lit up.
9To make a phone call or send a fax. 電話を入れる ("to give someone a call," often as advance notice) is still common; the fax-related use has become rarer as fax machines fall out of use.
到着する前に一本電話を入れておいた。
I gave them a call ahead of time before arriving.