noun, noun which may take the genitive case particle 'no'
division by 1000; one-thousandth
Used in mathematical or technical contexts to express a fraction or division into 1000 parts. Often appears in compounds like 千分率 (per mille).
千分の一の確率で当たる。
It hits with a probability of one in a thousand.
千分率はパーミルとも呼ばれる。
The rate per thousand is also called permille.