solemn
adj.adj. very serious and formal. You use this to describe someone who is not smiling or an event that is quiet and respectful.
adj. characterised by deep sincerity, formality, or gravity. Often describes facial expressions, ceremonies, or promises that are serious and dignified.
The judge spoke in a solemn voice.
The crowd fell silent as the soldiers began the solemn ceremony at the memorial.
The president took a solemn oath to uphold the constitution, aware that the eyes of the entire nation were fixed upon him during the transition of power.
From Middle English solempne, solemne (“performed with religious ceremony or reverence; devoted to religious observances, sacred; ceremonious, formal; of a vow: made under a religious sanction, binding; religious celebration, celebration of a feast day; famous, well-known; important; grand, imposing; awe-inspiring, impressive; grave, serious; dignified; enunciated or held formally”) [and other forms], from Old French solempne, solemne (“serious, solemn”) [and other forms], or from its etymon Late Latin sōlempnis, sōlennis, from Latin sōlemnis, from sollemnis (“appointed, established, fixed; common, customary, ordinary, ritual, traditional, usual; ceremonial, religious, solemn; festive; annual, yearly”) [and other forms]. The further etymology is uncertain; sollus (“entire, whole”) (ultimately from Proto-Indo-European solh₂- (“whole”)) + epulum (“banquet, feast”) (in the sense of a ritual; perhaps ultimately from Proto-Indo-European h₁ed- (“to eat”)) has been suggested.
Typically used to describe people, events, or spoken promises; often follows linking verbs like 'remain' or 'look'.