Noun seriousness has 3 senses
  1. earnestness, seriousness, sincerity - an earnest and sincere feeling
    --1 is a kind of gravity, solemnity
  2. seriousness, distressfulness - the quality of arousing fear or distress; "he learned the seriousness of his illness"
    --2 is a kind of badness, severity
  3. seriousness, earnestness, serious-mindedness, sincerity - the trait of being serious; "a lack of solemnity is not necessarily a lack of seriousness"- Robert Rice
    --3 is a kind of trait
    Antonyms: frivolity, frivolousness
    --3 has particulars:
     committedness, commitment; graveness, gravity, sobriety, soberness, somberness; sedateness, staidness, solemnity, solemness