How to say "rat" in Japanese

• ネズミJLPT N3approx.Common
  nounThe animal. Japanese does not distinguish rat from mouse: ネズミ covers both, so this is the word for the rodent itself, such as one seen in a house or on the street.
  猫ねこがいなくなるとネズミたちが遊あそびだす。↗

  When the cat is away, the mice will play.
• いぬJLPT N5approx.Common
  nounNot the animal: this is the figurative 'rat' — a derogatory word for an informer or snitch, someone who betrays others — used when angrily denouncing such a person.
  気きをつけて。警察けいさつの犬いぬがかぎ回まわってる。↗

  Watch out! A police spy is snooping around.

Use 「ネズミ」 for the animal — Japanese has one word covering both mice and rats — and 「いぬ」 only for the figurative 'rat', a derogatory term for an informer or betrayer.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• ねずみmouse
• 鼠ねずmouse
• ラッテrat (esp. a laboratory rat)
• ラットrat (esp. a laboratory rat)
• タレこむto tip off (e.g. the police)
• いぬsquealer