1. concerned with work or important matters rather than play or trivialities

- a serious student of history

- a serious attempt to learn to ski

- gave me a serious look

Similar word(s): earnest, sincere, solemn, grave, sedate, sober, overserious, real, thoughtful, sobering, solid

2. of great consequence

- marriage is a serious matter

Similar word(s): important

3. causing fear or anxiety by threatening great harm

- a serious wound

- a serious turn of events

Similar word(s): critical, dangerous, grave, grievous, severe

4. appealing to the mind

- a serious book

Similar word(s): intellectual, good

5. completely lacking in playfulness

Similar word(s): sober, unplayful

6. requiring effort or concentration; complex and not easy to answer or solve

- raised serious objections to the proposal

- the plan has a serious flaw

Similar word(s): difficult, hard

Sentences with serious as an adjective:

- It was a surprise to see the captain, who had always seemed so serious, laugh so heartily.

- This is a serious problem. We'll need our best experts.

- After all these years, we're finally getting serious attention.