Adjective

serious, grave, solemn, sedate, staid, sober, earnest mean not light or frivolous. serious implies a concern for what really matters.
// a serious play about social injustice grave implies both seriousness and dignity in expression or attitude.
// read the proclamation in a grave voice solemn suggests an impressive gravity utterly free from levity.
// a sad and solemn occasion sedate implies a composed and decorous seriousness.
// remained sedate amid the commotion staid suggests a settled, accustomed sedateness and prim self-restraint.
// a quiet and staid community sober stresses seriousness of purpose and absence of levity or frivolity.
// a sober look at the state of our schools earnest suggests sincerity or often zealousness of purpose.
// an earnest reformer