Japan-Akita, 1863, 9M 2B, JDNA 09-71 KM-12

Momme (匁, monme) is both a Japanese unit of mass and former unit of currency. As a measurement, Momme is part of a table of Japanese units where during the Edo period it was equal to 1⁄10 ryō (aka Tael). Since the Meiji era 1 momme has been reformed to equal exactly 3.75 grams in SI units.^[2] The latter term for Momme refers to when it was used as a unit of currency during the Edo period in the form of silver coins.^[2][3] As a term, the word "Momme" and its symbol "匁" are unique to Japan.^[2][4] The Chinese equivalent to Momme is qián (Chinese: 錢), which is also a generic word for "money".^[2][5] While the term Momme is no longer used for currency, it survives as a standard unit of measure used by pearl dealers to communicate with pearl producers and wholesalers.^[6]

The Japanese word Momme first appeared in a family book by the Ōuchi clan during the Bunmei era in 1484.^[7][8] In the English language the word first appears in the early 1700s per the Oxford English Dictionary, which first traces its usage to Johann Jakob Scheuchzer in 1727.^[9]