De-'oraita And De-rabbanan
The concepts of de-'oraita (Aramaic: דאורייתא) and de-rabbanan (Aramaic: דרבנן) are used extensively in discussion and text relating to Jewish law. The former refers to halachic requirements that are biblically mandated, while the latter refers to halachic requirements that are rabbinically mandated. In Aramaic, de-'oraita means "from the Torah" and de-rabbanan means from our Rabbis.
Examples of the application of these two terms abound. One such application appears in the laws relating to grace after meals. There are four blessings contained within the grace after meals, and while the first three are biblically mandated, the fourth blessing was added much later on in Jewish history and is rabbinically mandated (B. Brachot 45b) The first three blessings would thus be referred to as de-'oraita and the last blessing would be referred to as de-rabbanan. While this distinction had practical ramifications in the Talmudic era in terms of certain instances in which someone might be exempt from reciting the fourth blessing, these distinctions are now primarily academic.
Another example are the commandments regarding the famous phrase "Thou shall not boil a kid in its mother's milk." From this, many laws of kashrut are derived by the rabbis. One might think this would make it de-rabbanan because it was derived by the rabbis, but the laws are actually de-'oraita because they are derived by interpreting the Torah. On the other hand, the extension of this prohibition to eating chicken with milk is de-rabbanan as it is the product of a specific Rabbinic enactment.
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