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 …

SERIOUS definition: of, showing, or characterized by deep thought. See examples of serious used in a sentence.

Serious can be used to describe something that is significant, grave or of significant importance. It can be characterized by a lack of frivolity, playfulness, or lightheartedness. It often relates to …

Feb 21, 2026 · Adjective serious (comparative more serious, superlative most serious) Without humor or expression of happiness; grave in manner or disposition.

These adjectives refer to manner, appearance, disposition, or acts marked by absorption in thought, pressing concerns, or significant work. Serious implies a concern with responsibility and work as …

serious: Careful in thought, full of concern, or restrained and dignified in manner; somber or grave.

Definition of serious adjective in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.

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.