Solemn means deeply serious and dignified. A solemn occasion, a solemn promise, solemn faces.
It suits funerals, oaths and ceremonies, and a solemn promise is one made with full weight. In law, a solemn undertaking is given formally to a court. Of a child's expression it means seriously concentrated, which is affectionate. Note solemnly, which is used constantly in oaths — I solemnly swear; solemnity; and that solemn is not the same as sad, though the two often appear together.
1adjectivesolemnDeeply serious and dignified.
“The ceremony was a solemn occasion, and nobody spoke above a whisper.”
synonyms: grave, sombre
solemn is a quality of seriousness.
Also accepted in games: grave
Latin sollemnis meant customary or performed at a fixed date — from sollus, whole, plus annus, a year. A solemn rite was an annual one, and the seriousness came from the ceremony rather than the sorrow.
Proto-Indo-European
*solh₂-
Latin
sōlempnis
Old French
solempne
Middle English
solempne
English, today
solemn
Built from
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”)solem, solemp, solempe, solempn, sollempne, solom, solen, solenne, sollen, sollene, from Old French solempne, solemne (“serious, solemn”)solene, sollempne, or from its etymon Latin sōlempnis, sōlennis, from Latin sōlemnis, from sollemnis (“appointed, established, fixed; common, customary, ordinary, ritual, traditional, usual; ceremonial, religious, solemn; festive; annual, yearly”)sollennis, sollempnis. 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.
Etymology from Wiktionary, CC BY-SA