Solemnity

noun

1. The quality of being deeply serious and sober or solemn.

   "the solemnity of a funeral"

2. An instance or example of solemn behavior; a rite or ceremony performed with reverence.
3. A feast day of the highest rank celebrating a mystery of faith such as the Trinity, an event in the life of Jesus, the Virgin Mary, or another important saint.
4. A solemn or formal observance; proceeding according to due form; the formality which is necessary to render a thing done valid.
5. A celebration or festivity.