solemn

Serious and dignified: synonym: serious.

Showing or behaving with dignified restraint or earnestness.

Performed with full ceremony.

Made with deep sincerity or invoking the force of religion.

Dark or undecorated.

To solemnize.

Recurring yearly; annual.

Marked by religious rites or ceremonious observances; connected with religion; sacred; also, marked by special ritual or ceremony.

Pertaining to holiday; festive; joyous.