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
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
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
Some 182 people with serious mental illness in the city jails are waiting for one of those beds, city correction officials said Thursday.
—
Graham Rayman, New York Daily News, 29 June 2025
So far, the project has helped some counties reduce their administrative separation populations by up to 90% through limiting isolation to cases of recent violence and banning the use of restrictive housing for people with serious mental illness.
—Kelly Davis, San Diego Union-Tribune, 29 June 2025
An electric motorcycle bearing a Honda badge is bound to attract serious attention – and lately, the rumor mill has been buzzing.
—Utkarsh Sood
june 29, New Atlas, 29 June 2025
Even 6 inches of moving water can pose a serious risk of knocking you off your feet.
—Nc Weather Bot, Charlotte Observer, 29 June 2025
See All Example Sentences for serious
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Graham Rayman, New York Daily News, 29 June 2025
So far, the project has helped some counties reduce their administrative separation populations by up to 90% through limiting isolation to cases of recent violence and banning the use of restrictive housing for people with serious mental illness.
—Kelly Davis, San Diego Union-Tribune, 29 June 2025
An electric motorcycle bearing a Honda badge is bound to attract serious attention – and lately, the rumor mill has been buzzing.
—Utkarsh Sood
june 29, New Atlas, 29 June 2025
Even 6 inches of moving water can pose a serious risk of knocking you off your feet.
—Nc Weather Bot, Charlotte Observer, 29 June 2025
See All Example Sentences for serious
Cite this Entry
“Serious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/serious. Accessed 5 Jul. 2025.
Copy CitationKids 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
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