Ke'zayit

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Ke'zayit (Hebrew: כזית) is a Talmudic unit of volume approximately equal to the size of an average olive. The word itself literally means "like an olive." The rabbis differ on the precise definition of the unit:

• Rashi defines it as one-half of a beytza (a beytza is the volume of an egg).
• Rambam defines it as one-third of a beytza.
• According to some interpretations, including the Chazon Ish, the zayit is not related to other units by a fixed ratio, but rather should only be conceived of independently as the size of an average olive.

Its uses in halacha include:

• The minimal amount eaten of a food for the saying of Bracha Ahrona (the traditional grace after meals) to be required is a ke'zayit.
• If a person is exposed to at least a ke'zayit of the flesh of a dead body, he becomes ritually impure.

[edit] See also

• Ancient Hebrew units of measurement
• Olive (fruit)