The was a gold currency unit in the shakkanhà  system in pre-Meiji Japan. It was eventually replaced with a system based on the yen.
The ryà  was originally a unit of weight from China, the tael. It came into use in Japan during the Kamakura period. By the AzuchiâÂÂMomoyama period it had become nearly uniform throughout Japan, about 4.4 monme as a unit of weight (about the same as 16.5 grams).
During the Sengoku period, various local daimyà  began to mint their own money. One of the best known and most prestigious of these private coins was the kà Âshà «kin (ç²å·ÂéÂÂ, coin/gold of the Kà Âshà « Province) issued by warlord Takeda Shingen, who had substantial gold deposits within his territories. The value of the kà Âshà «kin was based on its weight, with one kà Âshà «kin equal to one ryà  of gold, and thus stamped with its weight (about 15 grams). The exchange rate fluctuated. A ryà  of gold was worth 3 kan (3000) copper coins around the 1530s, or early Tenbun era but fell to only somewhat stronger than the later fixed notion of "1000 mon" (copper coins), i.e., 1 ryà  = 1.2âÂÂ1.6 kan, by late Tenshà  era, or end of century.
The Tokugawa shogunate attempted to create a central currency, based on gold, silver and copper units all exchangeable at fixed rates. Oblong gold coins, called koban, were minted with one koban containing about one ryà  of gold, so that koban carried a face value of one ryà Â. The official rate was set in 1609 at one ryà  equal to 50 monme (approx 187 grams) of silver, or 4000 brass coins. However, in reality the relative values between gold, silver and brass currencies fluctuated on an almost daily basis throughout the Edo period.
In 1695 the government decided to increase the amount of metal money in circulation by debasement. As a result, the ryà  as a unit of weight of gold and the ryà  as the face value of the koban were no longer synonymous. The Keichà  koban issued after the monetary reform of May 1601 offered approximately 17.9 grams gold with fineness of 84âÂÂ87%. The Genroku koban issued in 1695 still weighed around 17.9 grams; however its gold content was reduced to 57%. The Hà Âei koban of 1706 returned to the original fineness; however, the size was much reduced and it had little more than half the metal value of the Keichà  koban. In 1700 the official exchange rate was adjusted to 1 ryà  equal to 60 monme silver (225 grams) or 4000 brass coins. Tokugawa Yoshimune further conducted a reform to stimulate the economy and raise prices in 1736, again lowering the gold content of the koban.
One ryà  was also considered equivalent to 1 koku of rice, or the amount of rice needed to feed one person for one year, although this was a less exact standard, which fluctuated depending on the abundance of the rice crop in any particular year.
On June 27, 1871, with the introduction of currency reforms after the Meiji Restoration, the ryà  was abolished, and replaced one-for-one with the Yen.
These fluctuations in the gold content of the koban over time, as well as differences in the cost of living between various points in the Edo period and in modern times make any attempt to relate the value of one ryà  in terms of modern currency very difficult. Japanese middle school textbooks often state that one ryà  was approximately equivalent to 100,000 Yen at the start of the Edo period, and around 3000âÂÂ4000 yen at the end of the Edo period. On the other hand, the Currency Museum of the Bank of Japan states that one ryà  had a nominal value equivalent 300,000âÂÂ400,000 yen, but was worth only 120,000âÂÂ130,000 yen in practice, or 40,000 yen in terms of rice.
As an independent sinogram, 両 is one of the kyà Âiku kanji, a jà Âyà  kanji taught in elementary school in Japan. It is a third-grade kanji and also means âÂÂbothâÂÂ.