solemn

/ˈsɑləm/
adjective
  1. Serious and without humor; showing deep sincerity or gravity.
    • The ceremony was quiet and solemn.
    • They made a solemn promise to protect the forest.
    • The judge had a solemn expression as she read the verdict.
  2. Formal and dignified, often in a religious or official context.
    • The graduation was a solemn occasion for the students.
    • The solemn music filled the cathedral.
    • He took a solemn oath to serve his country.