Shaku (a unit of volume in old Japanese system of weights and measures) ()

Shaku (勺) is a unit of volume in the East Asian system of weights and measures.

1 shaku is defined to have a 10th of 1 go (合), and a 100th of 1 sho (go and sho are also units of volume). In Japan, 1 sho is almost equal to 1.8039 liters, so 1 shaku is almost equal to 18.039 milliliters, and in China, 1 sho is equal to 1 liter, so 1 shaku is equal to 10 milliliters.

Originally, 'shaku' (in pinyin, 'shao') was a small cup with a long handle attached to its rim, and this cup seen in ancient China was for scooping up alcohol, and its capacity became the volume unit called shaku. Incidentally, the cup with its handle attached on its side or around its bottom was called to (斗; in pinyin, 'dou'), and this cup was for scooping up water. Shaku was linked with both sho and go, and 1 shaku was equalized with a 100th of 1 sho, and with a 10th of 1 go.

Therefore, when go began to have the second meaning of a 10th square measure of 1 tsubo (or 'bu'; 1 tsubo is almost equal to 3.305785 square meters), shaku also began to have the second meaning of a 10th square measure of 1 go (that is, a 100th square measure of 1 tsubo). And thirdly, go is also used as a length unit for a path up a mountain, and shaku, too, is used as a length unit of a 10th of 1 go.
But shaku here (written as 勺) is often confused with another length unit of the same reading (written as 尺), so it is not rare that 勺 is mistakenly written as 尺 such as 8 go and 5 shaku should be written as '八合五勺' in Chinese characters, but often, it is written as '八合五尺.'

[Original Japanese]