grave: dignified and somber in manner or character and committed to keeping promises; "a grave God-fearing man"; "a quiet sedate nature"; "as sober as a judge"; "a solemn promise"; "the judge was solemn as he pronounced sentence"
earnest: characterized by a firm and humorless belief in the validity of your opinions; "both sides were deeply in earnest, even passionate"; "an entirely sincere and cruel tyrant"; "a film with a solemn social message"
(solemnity) sedateness: a trait of dignified seriousness
(solemnly) in a grave and sedate manner; "the judge sat there solemnly"
A Solemnity of the Roman Catholic Church is a principal holy day in the liturgical calendar, usually commemorating an event in the life of Jesus, his mother Mary, or other important saints. The observance begins with the vigil on the evening before the actual date of the feast.
Deeply serious and somber; Somberly impressive; Performed with great ceremony; Sacred; Gloomy or sombre
(solemnity) The quality of being deeply serious and sober or solemn; An instance or example of solemn behavior
(solemnly) seriously, with awe.
Somberly or gravely impressive; mournful; grave; sad; glum; serious