The reverse side or underside of something; the side hidden from view.
洋服のタグは裏についていることが多い。
Clothing tags are often attached on the underside (the back).
紙の裏にメモを書いて渡した。
I wrote a note on the back of the paper and handed it over.
コインの裏には王様の顔が刻まれている。
The reverse side of the coin has the portrait of a king engraved.
The rear or back of something; the area located behind.
家の裏に小さな庭がある。
There is a small garden at the back of the house.
荷物は店の裏に置いてください。
Please leave the luggage at the back of the shop.
The lining or inside surface (e.g., of clothing).
このジャケットの裏はシルクでできている。
The lining of this jacket is made of silk.
コートの裏が寒さを防いでくれる。
The coat's lining protects against the cold.
Behind-the-scenes activity; offstage; things happening out of public view.
政治の世界では裏で多くの交渉が行われている。
In politics there are many negotiations carried out behind the scenes.
舞台裏では出演者が最終確認をしていた。
Backstage, the performers were doing final checks.
A hidden side; aspects not obvious from the surface (e.g., a person's hidden motives).
その会社には表に出ない裏があると噂されている。
There are rumours that the company has hidden matters behind the scenes.
彼の笑顔の裏には不安があった。
Behind his smile there was anxiety.
Proof or backing (colloquially used for evidence or corroboration of a claim).
その報道にはまだ裏が取れていない。
That report has not yet been corroborated.
記者は発表の裏を取るために関係者に確認した。
The reporter checked with insiders to verify the announcement.
Contrary or opposite (as in doing the opposite of what is expected); used in expressions like 裏をかく (to outwit).
彼は相手の裏をかいて奇襲を成功させた。
He outwitted the opponent and successfully launched a surprise attack.
計画を裏をかかれて失敗した。
Our plan failed because we were outsmarted.
The inverse or opposite of a hypothesis; the contrary outcome or evidence.
実験の結果は仮説の裏を示した。
The experimental results showed the opposite of the hypothesis.
データが理論の裏を取ったため、見直しが必要だ。
Because the data contradicted the theory, a review is necessary.
In baseball, the bottom (later half) of an inning (as opposed to the top, 表).
九回の裏に逆転ホームランが出た。
A go-ahead home run came in the bottom of the ninth.
三回の裏に相手チームが点を取った。
The opposing team scored in the bottom of the third.