What is the formal Hebrew name of Yom Kippur used in the Bible?

The formal Hebrew name of Yom Kippur used in the Bible is Yom HaKippurim.

The Hebrew phrase means “Day of the Atonements,” using the plural form kippurim. This biblical name appears in passages such as Leviticus 23, which commands observance of the tenth day of the seventh month as a sacred day of rest and self-denial. The name reflects the day’s central purpose: atonement and reconciliation through repentance, fasting, prayer, and, in the Temple era, sacrificial worship.

“Yom Kippur” is the familiar shortened form. The singular kippur became increasingly common in later Hebrew usage, while the biblical and classical formal expression retained kippurim. English translations often render the holiday simply as the “Day of Atonement.”

The name is not the same as Yom Teruah, the biblical name associated with the festival later commonly called Rosh Hashanah. Nor is it a modern Israeli national observance such as Yom HaAtzmaut. Today, Jewish communities mark the day primarily through a complete fast, extended prayer, confession, and reflection, since the ancient Temple sacrifices can no longer be performed.