solemnity
noun /səˈlemnəti/
  /səˈlemnəti/
- [uncountable] the quality of being solemn- He was smiling, but his eyes retained a look of solemnity.
- She handed him the envelope with mock solemnity.
- He was buried with great pomp and solemnity.
- I responded with due solemnity.
- The monument was unveiled with great solemnity.
 Oxford Collocations Dictionaryadjective- great
- mock
- due
- …
 - air
- sense
 - with solemnity
 
- solemnities[plural] (formal) formal things that people do at a serious event or occasion- to observe the solemnities of the occasion
 
Word OriginMiddle English (in the sense ‘observance of formality and ceremony’, frequently in the phrases in solemnity, with solemnity): from Old French solemnite, from Latin sollemnitas, from sollemnis ‘customary, celebrated at a fixed date’, from sollus ‘entire’.