wikipedia | Kosher foods are those that conform to the regulations of kashrut (Jewish dietary law). Food that may be consumed according to halakha(Jewish law) is termed kosher in English, from the Ashkenazi pronunciation of the Hebrew term kashér (כָּשֵׁר), meaning "fit" (in this context, fit for consumption). Food that is not in accordance with Jewish law is called treif (Yiddish: טרײף or treyf, derived from Hebrew טְרֵפָה trāfáh) meaning "torn."
A list of some kosher foods are found in the books of Leviticus 11:1-47 and Deuteronomy 14: 3-20, as are also certain kosher rules. Reasons for food not being kosher include the presence of ingredients derived from nonkosher animals or from kosher animals that were not slaughtered in a ritually proper manner, a mixture of meat and milk, wine and grape juice (or their derivatives) produced without supervision, the use of produce from Israel that has not been tithed, or the use of non-kosher cooking utensils and machinery. Every law of kashrut, according to all Rabbinic authorities of the ages in a rare agreement, makes the assertion that the laws can be broken when human life is at stake. Among the dozens of sources for the laws of pikuach nefesh (the Jewish term for saving any life) are the multiple discussions in the Talmud, for instance B. Yoma 83a, "We have agreed in the case of saving a soul he may be given [by a doctor in this case] to eat even unclean things, until his eyes are lightened from death".
