User:Nadav1/Torah weights and measures

This page is a key to all units of measurement that appear in the Torah and Halachic texts. Concepts appearing here are taken from the Hebrew Bible, the Mishnah, and the Talmud.

Below is a general background on the topic of Torah weights and measures, methods into their investigation, and Halachic questions which concern them. Afterwards is included a list of the different measures, their descriptions, and values of the measures in contemporary units.

Background
Whereas in our time there exist standardized international units, people in biblical and talmudic times frequently used common and easily available measures (e.g. the length of a finger). Hebrew units of length often have parallels in other ancient systems of measurement. Their traces can be found in systems that are still in use today.

The measures are divided into categories by the texts in which they first appear. The three categories comprise the biblical measures, the Tannaitic measures, and the Talmudic measures, which first appear in the Jerusalem or Babylonian Talmud.

Since the canonization of the Talmud, Halachic writings have employed measurements specific to their locales, but these lack singular Halachic significance; measures of every period were always converted into the traditional biblical and rabbinic measures used in Halacha.

It must be noted that in the biblical and Talmudic periods, many peoples used measures paralleling Halachic ones, though their definitions usually - and at times significantly - differed. For example, the length of a Roman foot differs by orders of magnitude from the Jewish/Halachic parsa despite the similarity in the literal meaning of the words. (This also occurs today with units such as the mile, whose meaning varies from place to place.)

The large number of measures, and the multiplicity of names for identical measures, is due to the fact that Halacha adopted the units in common usage in the different time periods and places in which it developed and spread. This is also the reason why a sizable number of the measures mentioned in the Mishnah and Talmud have no special Halachic use: they are only mentioned in examples and stories and are not used for specifying dimensions in any law. Nevertheless, in order to understand many cases described in rabbinic writings, one must know the dimensions of the different units and how to maneuver between them.

Types of measures
Measures are used in Halacha in various ways:
 * Units of length are used for measuring lengths and distances. Examples: dimensions of the Sukkah and Four Species, Techum Shabbat, distancing of plants to prevent cross-breeding
 * Units of volume are used for measuring foods and various liquids. Examples: forbidden and commanded foods, Mikvah and Ablution
 * Units of weight for measuring money and spices. Examples: Sums of money in laws of rape, Ketubah, Pidyon haBen, and Pidyon Maaser Sheni. Components of incense
 * Units of time for measuring durations of blessings and testimonies, astronomical calculations for the Hebrew Calendar, etc.
 * Units of area are defined in terms of length or volume units.

Halachic measures may be categorized as
 * Measuring devices common in biblical/Talmudic times (e.g. kaneh, hevel, kav, hin, saah)
 * Agreed values (mil, ris, parsah, dinar, shekel, sela)
 * Common Nature objects (e.g. etzbah, tephach, ama, kegrogeret, kezayit, kebeytzah)

Fractions of measures at times became names in themselves:
 * Fourth (revi'it) - a fourth of a log
 * Eighth (shminit) - an eighth of a log
 * Quarter (rova) - a fourth of a kav
 * Half (peres) - one half of a standard loaf (of bread)

Imprecision of measures and conversions between them
The fact that some of the measures are based on measuring devices, some on agreed values, and some on natural objects makes moving between the units difficult. Already in the Bible, we find testimony to the transfer between different units ( in weight: "twenty gerah - the shekel," "beka...half of the shekel, the shekel of holiness"; in volume: "and the omer - it is half of the eifah"), and in the talmudic writings we find many numbers juxtaposed as scalar factors for transferring between different units of measurement (for example, in volume: "the kave - four logs)