1.
house mouse (Mus musculus)
A small rodent of the species Mus musculus, the common house mouse. The Japanese name reflects the old folk belief that the mouse's gestation period is about twenty days. Widely kept as a laboratory animal and pet, and the basis of the white mouse used in scientific research.
Composed of 二十日 (twenty days) and 鼠 (mouse; rat). The name comes from the old folk belief that the mouse gives birth roughly twenty days after conception — actually closer to nineteen to twenty-one days, so the name is reasonably accurate.
Usage
The standard zoological and everyday name for the house mouse, distinct from the larger 鼠 (rat) that infests buildings. The white-coated laboratory strain is universally called 二十日鼠 or simply マウス (in scientific contexts). The katakana ハツカネズミ is also common in biology textbooks, pet shops, and pest control material. As a household pest the word 二十日鼠 is somewhat technical; speakers more often just say ねずみ.
Common collocations
- 二十日鼠を飼う: to keep mice (as pets or lab animals)
- 実験用二十日鼠: laboratory mouse
- 白い二十日鼠: white mouse
- 二十日鼠の巣: a mouse's nest
Similar words
- 鼠: mouse; rat — the broad category term, covers both mice and rats
- 溝鼠: brown rat (Rattus norvegicus) — a much larger urban rodent
- 熊鼠: black rat (Rattus rattus) — another common urban rat
- マウス: mouse — katakana loanword, used in lab and computing contexts
- 野鼠: field mouse — a generic term for wild mice that live outdoors