What is "gerah"

Gerah \Ge"rah\, n. [Heb. g?rah, lit., a bean.] (Jewish Antiq.) A small coin and weight; 1-20th of a shekel.

Note: The silver gerah is supposed to have been worth about three cents; the gold about fifty-four cents; the weight equivalent to about thirteen grains.

n. an ancient Hebrew unit of weight and currency equal to one twentieth of a shekel

A gerah Hebrew "גרה" is an ancient Hebrew unit of weight and currency, equivalent to one-twentieth of a shekel, a shekel being 180 barleycorns or 60 carob divided by 20 = 3 carob. This is 0.568 grams.

A gerah is in Aramaic a ma'ah "מעה" ( Mishnah Hebrew pl. ma'ot "מעות" which means "coins"). It was originally a fifth of a Denarius/ zuz, as seen in Exodus ("20 gerah is a shekel"), then became a sixth of a denar/Zuz, such as the Yehud coins which came in two denominations, approximately .58 gram as a ma'ah and approximately .29 gram as a half ma'ah (chatzi ma'ah), and (.58 X 6 = 3.48) which is about the weight of a Zuz/Denarius based on a 14 gram Shekel.

The Jerusalem Talmud Shekalim, in the Mishnah, debates if a kalbon, which was added when annually giving a half shekel to the Temple, was a "ma'ah" or a "chatzi ma'ah" (half ma'ah).