The term for the penitential prayers often recited before Rosh Hashanah is Selichot.
Selichot are Jewish prayers and liturgical poems focused on repentance, confession, forgiveness, and appeals to divine mercy. A central theme is the Thirteen Attributes of Mercy, a biblical passage from Exodus that describes God as compassionate and forgiving. The word can refer both to individual poems and to the broader prayer service in which they are recited.
The timing differs by Jewish rite. Sephardic communities commonly begin reciting Selichot during Elul, the Hebrew month preceding Rosh Hashanah. Ashkenazi communities generally begin on the Saturday night before Rosh Hashanah, or earlier when necessary to ensure several days of recitation. Services are often held late at night or before morning prayers.
Selichot are not limited to Rosh Hashanah. They are also associated with Yom Kippur and certain fast days. Kinnot are instead mourning poems, while Hoshanot are prayers associated especially with Sukkot, so neither is the general term for these pre–Rosh Hashanah penitential services.