1The reverse, opposite, or hidden side of an object; its underside or the side not normally seen.
洋服のタグは裏に付いていることが多い。
Clothing tags are usually attached on the inside (back).
紙の裏に電話番号をメモしておいた。
I jotted down the phone number on the back of the paper.
コインを裏返すと、建物の絵が描かれている。
When you flip the coin over, there's a picture of a building on the back.
2The rear or back area of a building or object; the part located behind rather than in front.
家の裏に小さな畑がある。
There's a small vegetable patch behind the house.
荷物はお店の裏に置いておいてください。
Please leave the delivery at the back of the store.
3The inner lining of clothing or a similar item.
このコートは裏がフリースで暖かい。
This coat is warm because the lining is fleece.
裏に名前を書いておくと忘れ物のとき安心だ。
Writing your name on the lining gives peace of mind if the item gets lost.
4Something happening out of public view; behind the scenes or offstage.
舞台裏では次の準備が慌ただしく進んでいた。
Backstage, preparations for the next part were proceeding in a rush.
その決定の裏には長い交渉があった。
Behind that decision was a long series of negotiations.
5A hidden aspect of a person or matter that isn't obvious on the surface.
彼の優しさの裏には厳しい過去があった。
Behind his kindness lay a difficult past.
あの話には何か裏があるような気がする。
I feel like there's more to that story than meets the eye.
6Evidence confirming that a claim is true; often used in the phrase 裏を取る (to verify).
記者はその情報の裏を取ってから記事にした。
The reporter verified the information before writing the article.
そのうわさにはまだ裏が取れていない。
That rumor hasn't been confirmed yet.
7The opposite of what was expected; used in the expression 裏をかく (to outwit / catch someone off guard).
相手の裏をかいて、逆方向に走った。
He outwitted his opponent by running the opposite way.
予想の裏をかく結果に、みんな驚いた。
Everyone was surprised by the result, which was the opposite of what was expected.
8In logic, the inverse of a proposition — formed by negating both the hypothesis and the conclusion.
「命題の裏」は必ずしも真とは限らない。
The inverse of a proposition is not necessarily true.
9In baseball, the bottom half of an inning (when the home team bats); the counterpart of 表 (the top).
9回裏に劇的な逆転サヨナラ本塁打が出た。
A dramatic game-winning home run came in the bottom of the ninth.
3回裏の攻撃で3点を追加した。
They added three runs in the bottom of the third.