A solemnity is a feast day of the highest rank in the liturgical calendar of the Roman Rite, celebrating a mystery of faith such as the Trinity, an event in the life of Jesus, his mother Mary, or another important saint. The observance begins with the vigil on the evening before the actual date of the feast. Unlike feast days of the rank of feast (other than feasts of the Lord) or those of the rank of memorial, solemnities replace the celebration of Sundays outside Advent, Lent, and Easter (those in Ordinary Time).
The word comes from Latin sollemnitas, derived from sollus (whole) and annus (year), indicating an annual celebration.
The solemnities of Nativity of the Lord, the Epiphany, the Ascension, and Pentecost are outranked only by the Paschal Triduum.
Other solemnities inscribed in the General Roman Calendar give way also to the following celebrations:
Solemnities inscribed in particular calendars yield not only to these, but also to the Commemoration of All the Faithful Departed.
With the exceptions noted in the table below regarding the solemnities of Saint Joseph and the Annunciation of the Lord, a solemnity that falls on the same day as a celebration of higher rank is transferred to the next day not occupied by a solemnity, a Sunday or a feast.
Among solemnities inscribed in the General Roman Calendar, those of the Lord have precedence over those of the Blessed Virgin and these latter over solemnities of other saints. Thus if, for instance, the Solemnity of the Sacred Heart of Jesus coincides with that of the Nativity of Saint John the Baptist or that of Saints Peter and Paul, it is these that are transferred to the next free day.