The Japanese word for "Rat" is nezumi ネズミ.
- Rat vs. nezumi ネズミThe word nezumi can refer to all sorts of rodents, rats and mice. And even some animals that aren't technically rodents but look like rodents.
- Common Nezumihatsuka-nezumi ハツカネズミ refers to the common House Mouse, while dobu-nezumi 溝鼠 refers to the common Brown Rat.
- mausu usually refers to mice used in laboratory experiments. It's also the only "mouse" word that refers to a computer mouse.
- ratte usually refers to a pet rat or mouse, or a lab rat.
The word "Rat" katakanized would be ratto ラット.
Beware: some kanji that are difficult to handwrite are easy to type on the computer, which may skew the usage statistics.