sol·emn 
(sŏləm)
(sŏləm)adj.
1.
a. Serious and dignified: a solemn occasion. See Synonyms at serious.
b. Showing or behaving with dignified restraint or earnestness: "Spade's face was solemn except for wrinkles at the corners of his eyes" (Dashiell Hammett).
2. Performed with full ceremony: a solemn High Mass.
3. Made with deep sincerity or invoking the force of religion: a solemn vow.
4. Dark or undecorated: a solemn forest; a solemn hall.
[Middle English solemne, from Old French, from Latin sollemnis, established, customary; see sol- in the Appendix of Indo-European roots.]
solemn·ly adv.
solemn·ness n.