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one-thousandth; 0.03 mm (one-thousandth of a sun); 0.01 percent (one-thousandth of a wari); 3.75 milligrams (one-thousandth of a monme)
old monetary unit (0.0001 yen)
一毛の差で負けてしまった。
I lost by a hair's breadth.
毛の単位は非常に小さいです。
The mou unit is extremely small.
毛は寸の千分の一の長さです。
A mou is one-thousandth of a sun.