Translation guide
The English word "rat" can refer to the animal, a traitor or informant, or be used in various idioms. This guide covers how to express these meanings naturally in Japanese.
Referring to the animal, especially the common brown or black rat.
General word for rat or mouse. Often written in katakana as ネズミ for clarity. Context usually distinguishes rat from mouse; if needed, specify with ドブネズミ (brown rat) or クマネズミ (black rat).
台所に鼠が出た。
A rat appeared in the kitchen.
鼠がチーズをかじっている。
A rat is nibbling on the cheese.
Loanword from English, often used in scientific or pet contexts, or to specifically mean a rat (as opposed to a mouse).
実験用のラットを飼育している。
We are breeding lab rats.
A person who betrays others by giving information to authorities or enemies.
General term for a traitor or betrayer. Can be used in criminal or personal contexts.
彼は仲間を警察に売った裏切り者だ。
He's a rat who sold out his friends to the police.
Specifically an informant or whistleblower, often to authorities. More formal than 裏切り者.
密告者が組織の秘密を警察に流した。
The rat leaked the organization's secrets to the police.
Spy, but can be used for a rat in the sense of someone secretly working for the other side.
Slang for a tattletale or snitch, often used by children or in casual contexts. From チクる (to snitch).
あの子はすぐ先生に言うチクリ魔だ。
That kid is a rat who always tells the teacher.
To suspect something is wrong or that someone is being dishonest.
Literally 'to think something is suspicious'. Natural equivalent for 'smell a rat'.
彼の話を聞いて、何か怪しいと思った。
When I heard his story, I smelled a rat.
To feel something is fishy or dubious. うさん臭い means suspicious-looking or shady.
その取引はどうもうさん臭いと感じた。
I smelled a rat about that deal.
A way of life in which people compete aggressively for wealth, status, or power.
Literally 'competitive society'. Often used to describe the rat race.
彼は競争社会から抜け出して田舎に引っ越した。
He got out of the rat race and moved to the countryside.
Competition for career advancement, specifically the corporate rat race.
彼は出世競争に疲れてしまった。
He got tired of the rat race.
Do not use 鼠 (ねずみ) to mean a traitor or informant. While 鼠 can metaphorically refer to a petty thief or sneak in some contexts, it is not the standard translation for 'rat' in the sense of an informant. Use 裏切り者 or 密告者 instead.
That guy is a rat working for the enemy.