Yom Kippur (ˌjɒm_kɪˈpʊər,_ˌjɔːm_ˈkɪpər,_ˌjoʊm-; יוֹם כִּפּוּר, Yōm Kippūr, ˈjom kiˈpuʁ, Day of Atonement) is the holiest day in Judaism and Samaritanism. It occurs annually on the 10th of Tishrei, corresponding to a secular date in September or early October.
Primarily centered on atonement and repentance, the day's main observances consist of full fasting and ascetic behavior accompanied by long prayer services in synagogue, as well as sin confessions.
Yom Kippur is the only day when fasting is permitted on Shabbat.
Alongside the related holiday of Rosh Hashanah, Yom Kippur is one of the two components of the "High Holy Days" of Judaism. It is also the last day of the Ten Days of Repentance.
The formal Hebrew name of the holiday is Yom HaKippurim, "day [of] the atonement". This name is used in the Bible, Mishnah, and Shulchan Aruch. The word kippurim (atonement) is one of many Biblical Hebrew words which, while using a grammatical plural form, refers to a singular abstract concept.
Beginning in the classical period, the singular form kippur began to be used in piyyut, for example in Unetanneh Tokef, alongside the standard plural form kippurim. Use of kippur spread In the medieval period, with Yom Kippur becoming the holiday's name in Yiddish and Kippur in Ladino. In modern Hebrew, Yom Kippur or simply Kippur is the common name, while Yom HaKippurim is used in formal writing.
In older English texts, the translation "Day of Atonement" is often used.
Yom Kippur is one of the two High Holy Days, or Days of Awe (Hebrew yamim noraim), alongside Rosh Hashana (which falls 9 days previously). According to Jewish tradition, on Rosh Hashanah God inscribes each person's fate for the coming year into the Book of Life, and waits until Yom Kippur to "seal" the verdict. This process is described dramatically in the poem Unetanneh Tokef, which is recited on Rosh Hashanah and Yom Kippur:
A great shofar will be blown, and a small still voice will be heard. The angels will make haste, and be seized with fear and trembling, and will say: "Behold, the day of judgment!".