serious
serious — adjective
1. describes a situation, event, or problem that is bad enough to cause real worry
describes a situation, event, or problem that is bad enough to cause real worry or danger
A serious fire broke out in the factory, forcing everyone to leave the building.
serious + disaster noun (fire / accident / storm)
Owen knew the problem was serious when the manager called an urgent meeting.
The company is in serious financial trouble and may have to close its doors.
collocation: serious financial trouble / serious problem
Yumi's cough grew serious, so her mother took her to see a doctor right away.
A serious accident on the highway shut down traffic for almost three hours.
- serious damage
- serious injury
- serious problem
- serious crime
- serious accident
- serious trouble
- minor
describes small, unimportant problems that cause little worry
Grammar Patterns
serious + noun (damage/problem/accident)
be + serious
Usage Note
Commonly placed before disaster or trouble nouns: fire, accident, injury, damage, problem, crime. Describes things with lasting bad effects, not everyday minor issues.
Common Mistakes
2. used to describe a health problem that is very bad and could put a person's life
used to describe a health problem that is very bad and could put a person's life in danger
A serious lung infection kept Christopher in the hospital for almost two weeks.
serious + illness noun (infection / disease / condition)
The doctors told Shirin that her grandmother's condition was serious but stable.
Patients with serious heart disease often need to change what they eat and drink.
Apinya's uncle was in a serious condition after surgery, so the nurses watched him closely.
pattern: in a serious condition — used by medical staff
A serious illness kept Valentina away from school for the rest of the term.
- serious illness
- serious condition
- serious infection
- serious disease
- serious injury
- stable
used by doctors to say the patient's condition is not getting worse
Grammar Patterns
serious + illness/disease/infection
condition is serious
Usage Note
Used primarily in medical contexts. 'Seriously ill' (adverb + adjective) is the more common form in everyday speech when talking about a person directly.
3. meaning what you say and not just pretending, lying, or trying to be funny
meaning what you say and not just pretending, lying, or trying to be funny
Dylan was not joking — he really meant what he said about moving to Japan.
be serious = not joking, common in spoken English
When Ishaan said he would quit his job, everyone thought he was being serious.
Are you serious about joining the army after you finish high school?
Are you serious? — common question to check sincerity
When Nadia said she was moving to Brazil, her brother asked if she was serious.
asked if + someone + was serious — checking sincerity
- be serious
- Are you serious?
- deadly serious
- be serious about
Grammar Patterns
be serious
Are you serious?
be serious about + noun/gerund
Usage Note
Often used in questions (Are you serious?) and in negative statements (I'm not serious). Takes the preposition 'about' when introducing the topic.
Common Mistakes
4. describes someone who tends to think carefully and behave in a calm, sensible wa
describes someone who tends to think carefully and behave in a calm, sensible way rather than being playful or silly
Quinn is a quiet, serious boy who spends most of his time reading books.
serious + person noun — describes character
The librarian had a serious expression that made the children speak softly.
Sofie's older sister is more serious than she is and rarely laughs at silly jokes.
Even at parties, Minho looks serious and seems to be thinking about something important.
The judge spoke in a serious voice, and everyone in the court listened closely.
serious + voice/expression/tone — describes manner
- serious person
- serious face
- serious expression
- serious voice
- serious manner
- sober
suggests a calm, restrained manner without humour
- solemn
more formal and dignified; suggests gravity and formality
- thoughtful
focuses on the habit of thinking deeply rather than the lack of humour
Grammar Patterns
serious + person/look/expression/voice/face
be serious
Usage Note
Describes a person's character, expression, or tone. Implies focus and intelligence, not unfriendliness. Often carries a neutral or slightly positive meaning.
Common Mistakes
5. putting a lot of time, thought, and effort into something because you believe it
putting a lot of time, thought, and effort into something because you believe it is important
Yuna is serious about becoming a dancer and practises for hours every single day.
be serious about + gerund (pursuing a goal)
The team made a serious effort to improve their performance this season.
Hassan is a serious runner who trains every morning even when the weather is bad.
If you are serious about learning guitar, you need to practise every day.
The school launched a serious campaign to reduce the amount of plastic waste.
serious + effort/campaign/attempt — significant, not casual
- serious about
- serious effort
- serious attempt
- serious student
- serious runner
- determined
emphasises not giving up despite difficulties
- dedicated
suggests loyalty and long-term devotion to a goal
- committed
implies a strong sense of promise and responsibility
- half-hearted
not putting in real effort or energy
Grammar Patterns
be serious about + noun/gerund
serious + effort/attempt/student
Usage Note
Always takes 'about' when specifying the activity: 'serious about [noun/gerund]'. Used positively to show dedication and commitment.
Common Mistakes
6. describes a romantic couple who are committed to staying together over a long pe
describes a romantic couple who are committed to staying together over a long period, possibly leading to marriage
After dating for two years, Tariq and his girlfriend decided to get serious.
get serious — become committed in a romantic relationship
Paloma told her parents her boyfriend was serious about her and wanted to meet them.
Indra wants a serious relationship, not just someone to go on casual dates with.
When a couple is serious, they often talk about where they want to live together.
be serious (about each other) = planning a shared future
Imani and her partner have a serious relationship and plan to get married next year.
- serious relationship
- get serious
- be serious about each other
- serious couple
- committed
broader in use; can apply to any relationship, goal, or promise
- casual
describes a relationship with no long-term plans or deep commitment
Grammar Patterns
be serious about each other
serious relationship
get serious
Usage Note
Only used for romantic relationships. 'Be serious about each other' and 'get serious' are the standard patterns. Not used for friendships or family relationships.
7. requiring careful thought or effort because the topic or activity is important,
requiring careful thought or effort because the topic or activity is important, rather than being something done just for enjoyment.
The students held a serious discussion about climate change and its effects.
collocation: serious discussion
Learning Mandarin is a serious commitment that takes years of practice.
collocation: serious commitment
The museum's collection deserves serious study by art historians.
passive construction: deserves serious study
Greta and her partner need a serious conversation about their future plans.
collocation: serious conversation
Buying a house is a serious decision that should not be made quickly.
collocation: serious decision
- serious discussion
- serious conversation
- serious decision
- serious commitment
- serious study
- serious work
- serious matter
- serious about + [noun/gerund]
- important
broader in meaning; can refer to events that matter rather than activities requiring mental focus
- significant
more formal; often describes impact or consequence rather than the effort demanded
- weighty
more formal; suggests heavy responsibility or profound implications
Grammar Patterns
serious + noun
be serious about + noun/gerund
Common Mistakes
8. to a very great or impressive degree; used to emphasise how large, strong, or in
to a very great or impressive degree; used to emphasise how large, strong, or intense something is, whether negative or positive.
The earthquake caused serious damage to buildings across the town.
collocation: serious damage
Valentina has serious doubts about accepting the job offer.
collocation: serious doubts
The restaurant near the station charges serious prices for simple food.
collocation: serious prices (informal)
Karim has serious talent as a violinist even though he is only twelve.
collocation: serious talent
There is serious concern among parents about the new safety rules.
collocation: serious concern
- serious damage
- serious doubt(s)
- serious concern
- serious problem
- serious money
- serious talent
- serious risk
- serious threat
- serious amount / number / degree
- severe
more restricted to negative contexts such as injury, weather, or punishment
- extreme
stronger in tone; suggests the upper limit of what is possible
- considerable
more formal and neutral; lacks the emotional weight of 'serious'
Grammar Patterns
serious + noun (damage, doubt, concern, talent, money)
Usage Note
Often describes the extent of something negative (damage, doubt, concern), but can also refer to impressive positive qualities (talent, money, skill).
Common Mistakes
9. of very high quality or standard; excellent in its kind, used in informal langua
of very high quality or standard; excellent in its kind, used in informal language to express admiration.
The jazz band at the festival played some serious music last night.
informal positive: serious music
Naoko makes serious sushi — the freshest fish in the whole market.
colloquial: serious + food type
That little café near the library serves a serious cup of coffee.
informal pattern: a serious cup of [drink]
Kwame drives a serious car that people stop to photograph.
- serious music
- serious food
- serious coffee / drink
- serious car
- serious gear / equipment
- excellent
standard and formal; suitable for any register
- top-notch
informal like 'serious'; more common in American English
- impressive
focuses on the effect the thing has on the observer rather than objective quality
Grammar Patterns
serious + noun (music, food, car, coffee)
Common Mistakes
Word family
- seriouslyadverbB1
- seriousnessnounB2
- nonseriousadjectiveB2
Synonym discussion
Sense: adjective/1
All five words describe something weighty, but they differ in scope and register. 'Serious' is the most general — it covers bad situations (serious accident), sincerity (serious offer), and personality. 'Severe' is narrower and more clinical, used for extreme weather, punishment, pain, or medical conditions (severe burns, severe penalties). 'Grave' is more formal and dramatic, reserved for situations with potentially fatal consequences (grave danger, grave mistake). 'Solemn' applies only to tone or atmosphere — a solemn ceremony or a solemn promise — and never to injury or crime. 'Earnest' describes a person's sincere, heartfelt attitude (an earnest request), not the situation itself. If you say 'a solemn warning,' the focus is on the speaker's serious tone; if you say 'a grave warning,' the focus is on the real danger being announced.
Common collocations
Nouns
- serious matter
- serious business
- serious case
- serious side
Adverbs
- deadly serious
- dead serious
- quite serious
- extremely serious
- very serious
- really serious
Phrases
- take something seriously
- in all seriousness
Prepositions
- serious about
Etymology
From Latin 'serius' (grave, earnest), passed through Old French 'serieux' into Middle English in the 15th century. The original meaning was 'earnest, weighty, not trifling' — a sense that remains at the core of the word today, although it later expanded to describe intensity, medical danger, and informal high quality.