staidness

The quality or state of being staid; seriousness; steadiness; sedateness; regularity; -- the opposite of wildness, or levity.

If sometimes he appears too gay, yet a secret gracefulness of youth accompanies his writings, though the staidness and sobriety of age be wanting.

Syn. -- Sobriety; gravity; steadiness; regularity; constancy; firmness; stability; sedateness.

noun

High seriousness of manner or bearing: graveness, gravity, sedateness, sobriety, solemnity, solemnness. See attitude/good attitude/bad attitude/neutral attitude, heavy/light, style/good style/bad style.

The noun has one meaning:

Meaning #1: a trait of dignified seriousness
  Synonyms: sedateness, solemnity, solemness