Gerah
A gerah Hebrew "גרה" is an ancient Hebrew unit of weight and currency, which, according to the Bible, Exodus, 30:13, was equivalent to 1/20th of a shekel. God tells Moses, the payment for life ransom during the census taking is 1/2 a shekel, "which weighs ten gerahs". This would make a whole shekel equal to 20 gerahs.
A gerah is in Aramaic a ma'ah "מעה". It was originally a fifth of a Denarius/zuz, as seen in Exodus, 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, and 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".
