Translation guide
The English word "inside" can refer to physical interior spaces, internal states, time limits, and more. This guide helps you choose the right Japanese expression for each meaning.
Expressing that something is located within a physical space, building, room, or container.
The most common and versatile word for 'inside'. Used for physical interiors of spaces, containers, and objects.
箱の中に猫がいます。
There is a cat inside the box.
部屋の中は暖かいです。
It's warm inside the room.
More formal and often used for the interior of buildings, organizations, or systems. Can sound technical.
建物の内部は撮影禁止です。
Photography is prohibited inside the building.
Emphasizes the inner side or surface of something, often contrasted with 'outside' (外側).
ドアの内側に鍵がかかっています。
The door is locked from the inside.
Expressing that something happens or is completed within a certain period or limit.
Used after a time expression to mean 'within' that period. Often used with deadlines.
1時間以内に戻ります。
I'll be back inside an hour.
今週中にレポートを提出してください。
Please submit the report inside this week.
Means 'while still within' a period. Implies doing something before the period ends.
明るいうちに帰りましょう。
Let's go home while it's still light (inside the daylight hours).
Referring to one's inner mental or emotional state, not visible externally.
Literally 'inside one's heart/mind'. Used for emotions, thoughts, or secrets.
心の中では怒っていました。
Inside, I was angry.
彼は心の中で笑った。
He laughed inside.
More formal, often used in expressions like 'secretly' or 'inwardly'.
Referring to privileged information or being a member of an organization.
Used for internal matters of a company or group. '内部情報' means inside information.
内部の人間しか知らない情報です。
It's information only insiders know.
Describing something turned so the inner surface becomes the outer surface.
Means 'inside out' for clothing or objects. Also used metaphorically.
シャツを裏返しに着ていますよ。
You're wearing your shirt inside out.
Referring to the interior of a living body, such as organs or stomach.
Formal/medical term for 'inside the body'.
体内時計が乱れています。
My internal clock is out of sync.
Casual way to say 'inside the stomach/belly'.
お腹の中で赤ちゃんが動いた。
The baby moved inside my belly.
While 中 (なか) is the most common translation, it is not always natural. For time limits, use 以内. For internal feelings, 心の中 is better. For inside out, use 裏返し.
中 (なか) is the general word for physical inside. 内 (うち) often means 'within' a group, home, or abstract boundary. 内部 (ないぶ) is formal and used for organizations or structures.
内心ではほっとした。
Inside, I felt relieved.
Loanword for 'insider', often used in financial contexts.
インサイダー取引は違法です。
Insider trading is illegal.
To turn something inside out or upside down. More forceful.
ポケットをひっくり返して見せてください。
Please turn your pockets inside out and show me.