A ta'anit or ta'anis (Mishnaic Hebrew: תענית) is a fast in Judaism in which one abstains from all food and drink, including water. Purposes A Jewish fast may have one or more purposes, including: Atonement for sins: Fasting is not considered the primary means of acquiring atonement; rather, sincere regret for and rectification of wrongdoing is key. Nevertheless, fasting is conducive to atonement, for it tends to precipitate contrition. Therefore, the Bible requires fasting on Yom Kippur. Because, according to the Hebrew Bible, hardship and calamitous circumstances can occur as a result of sin, fasting is often undertaken by the community or by individuals to achieve atonement and avert catastrophe. Most of the Talmud's Tractate Ta'anit ("Fast[s]") is dedicated to the protocol involved in declaring and observing fast days. Commemorative mourning: Most communal fast days that are set permanently in the Jewish calendar serve this purpose. These fasts include: Tisha B'Av, the Seventeenth of Tammuz, the Tenth of Tevet, and the Fast of Gedalia. The purpose of a fast of mourning is the demonstration that those fasting are impacted by and distraught over earlier loss. This serves to heighten appreciation of that which was lost. Supplication, such as the Fast of Esther Commemorative gratitude: Since food and drink are corporeal needs, abstinence from them serves to provide a unique opportunity for focus on the spiritual. Indeed, the Midrash explains that fasting can potentially elevate one to the exalted level of the ministering angels. This dedication is considered appropriate gratitude to God for providing salvation. Additionally, by refraining from such basic physical indulgence, one can more greatly appreciate the dependence of humanity on God, leading to appreciation of God's beneficence in sustaining His creations. Jewish fast days Full fast A Jewish full fast lasts from sunset to darkness the following night. There are two Jewish full fast days: Yom Kippur - the only fast day mentioned in the Torah (Leviticus 23:26-32) Tisha B'Av The two full fast days carry four restrictions in addition to eating and drinking - one may not wash his body, wear leather shoes, use colognes, oils or perfumes, or have sexual relations. Yom Kippur also has all the restrictions of Shabbat, and Tisha B'Av has restrictions somewhat similar to a mourner sitting shiva. The Halakha status of the two Jewish full fasts is that they are obligatory. Minor fasts Minor fasts are observed from dawn to nightfall,