serious

adjective

se·​ri·​ous ˈsir-ē-əs 

1

: thoughtful or subdued in appearance or manner : sober

a quiet, serious girl

2

a

: requiring much thought or work

serious study

b

: of or relating to a matter of importance

a serious play

3

a

: not joking or trifling : being in earnest

a serious question

b

archaic : pious

c

: deeply interested : devoted

a serious musician

4

a

: not easily answered or solved

serious objections

b

: having important or dangerous possible consequences

a serious injury

5

: excessive or impressive in quality, quantity, extent, or degree

serious stereo equipment

making serious money

serious drinking

seriousness noun

Synonyms of serious

• solemn
• severe
• earnest
• stern
• professional

Choose the Right Synonym for serious

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

Examples of serious in a Sentence

“You sound terrible.” “It's just a bad cold. Nothing serious.”

For my brother, not going to college was a serious mistake.

Crime is a serious problem in this neighborhood.

The team is a serious contender for the championship.

If you want to quit smoking, you have to make a serious effort.

They had a serious conversation about their relationship.

a serious novel about modern life

The story raises serious questions about our system of justice.

Dog shows are a serious business.

She is a serious cyclist who rides 200 miles each week.

Recent Examples on the Web

Two victims were airlifted to a hospital with serious or life-threatening injuries, police said, and a third victim died while being transported to the hospital. —Alexandra Koch , Michael Sinkewicz, FOXNews.com, 11 Feb. 2026

Ukraine’s President Volodymyr Zelensky said the attack showed Russia was not serious about peace. —Ivana Kottasová, CNN Money, 11 Feb. 2026

For serious symptoms, like difficulty breathing or rash with a fever, get immediate medical attention. —Ruth Jessen Hickman, Health, 10 Feb. 2026

Petal Kaddu is serious about eliciting high fives from passing fans—and isn't deterred by the steady rain over Wembley Way, between Wembley Park station and the UK's iconic national stadium. —Toby Skinner, Condé Nast Traveler, 10 Feb. 2026

Word History

Etymology

Middle English seryows, from Anglo-French or Late Latin; Anglo-French serious, from Late Latin seriosus, alteration of Latin serius weighty, serious; probably akin to Old English swǣr heavy, sad

First Known Use

15th century, in the meaning defined at sense 1

Phrases Containing serious

• can't be serious
• serious-minded

Rhymes for serious

• cereus
• nereus
• sirius
• deleterious
• delirious
• imperious
• mysterious

Kids Definition

serious

adjective

se·​ri·​ous ˈsir-ē-əs 

1

: thoughtful or quiet in appearance or manner

2

a

: requiring much thought or work

serious study

b

: of or relating to a matter of importance

a serious novel

3

: not joking or funny

4

: having important or dangerous possible consequences

a serious injury

seriously adverb

seriousness noun

Medical Definition

serious

adjective

se·​ri·​ous ˈsir-ē-əs 

: having important or dangerous possible consequences

a serious injury