Serious, grave, solemn, sedate, staid, sober, earnest mean not light or frivolous. Serious implies a concern for what really matters. Please don't laugh - i'm being serious.
He was wearing a very serious expression and i knew something was wrong. On the surface it's a very funny novel but it does have a more serious. See examples of serious used in a sentence.
Serious implies a concern with responsibility. Definition of serious adjective in oxford advanced learner's dictionary. If someone is serious about something, they are sincere about what they are saying, doing, or intending to do.
You really are serious about this, aren't you? Any important situation is serious, and this word is also the opposite of humorous and playful.