Synonyms and related words :
decorousness, demureness, earnestness, formality, frown, glower, gravity, grimace, grimness, lower, moue, mow, pout, scowl, sedateness, seriousness, sober-mindedness, soberness, sobersidedness, sobersides, sobriety, solemnity, solemnness, somberness, staidness, straight face, thoughtfulness, weightiness, wry face