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).
A rat appeared in the kitchen.
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).
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.
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.
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).
That kid is a rat who always tells the teacher.
To suspect something is wrong or that someone is being dishonest.
A way of life in which people compete aggressively for wealth, status, or power.
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.
The rat leaked the organization's secrets to the police.
That guy is a rat working for the enemy.
I smelled a rat about that deal.