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

Hu Haijun, the director of the Shanxi Bureau of the National Mine Safety Administration, is suspected of serious violations of discipline and law, the government’s Central Commission for Discipline Inspection said Monday evening. — ABC News, 14 July 2026

Grab bars — rails attached to walls, particularly in bathrooms — help provide balance and prevent falls, preventing serious injuries, said Jim Christian, founder of the effort to push Medicare to cover the devices, Safety Bars for America. — Panashe Matemba-Mutasa, Mercury News, 13 July 2026

Others will argue, reasonably, that no other commercial industry staffs onboard physicians on most routes, and that the infrequency of serious events makes dedicated medical staffing hard to justify economically. — Sriman Swarup, STAT, 13 July 2026

These leak spots can lead to serious moisture and mold issues, Meagher says. — Olivia McIntosh, Martha Stewart, 13 July 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

• 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