serious

[seer-ee-uhs]

adjective

1. of, showing, or characterized by deep thought.

2. of grave or somber disposition, character, or manner.

   a serious occasion; a serious man.

   Synonyms: staid, sedate, sober

3. being in earnest; sincere; not trifling.

   His interest was serious.

   Antonyms: trifling, frivolous

4. requiring thought, concentration, or application.

   serious reading; a serious task.

5. weighty or important.

   a serious book; Marriage is a serious matter.

   Synonyms: grave, momentous
   Antonyms: trivial

6. giving cause for apprehension; critical.

   The plan has one serious flaw.

7. Medicine/Medical.,  (of a patient's condition) having unstable or otherwise abnormal vital signs and other unfavorable indicators, as loss of appetite and poor mobility: patient is acutely ill.

noun

1. that which is of importance, grave, critical, or somber.

   You have to learn to separate the serious from the frivolous.

serious

/ ˈsɪərɪəs /

adjective

1. grave in nature or disposition; thoughtful

   a serious person

2. marked by deep feeling; in earnest; sincere

   is he serious or joking?

3. concerned with important matters

   a serious conversation

4. requiring effort or concentration

   a serious book

5. giving rise to fear or anxiety; critical

   a serious illness

6. informal,  worthy of regard because of substantial quantity or quality

   serious money

   serious wine

7. informal,  extreme or remarkable

   a serious haircut

Other Word Forms

• seriousness noun
• half-serious adjective
• half-seriously adverb
• nonserious adjective
• nonseriously adverb
• overserious adjective
• overseriously adverb
• quasi-serious adjective
• quasi-seriously adverb
• superserious adjective
• superseriously adverb
• ultraserious adjective
• ultraseriously adverb
• unserious adjective
• unseriously adverb

Word History and Origins

Origin of serious¹

First recorded in 1400–50; late Middle English, from Middle French serieux and Latin sērius “grave, earnest” or Late Latin sēriōsus; -ous, -ose ¹

Word History and Origins

Origin of serious¹

C15: from Late Latin sēriōsus, from Latin sērius; probably related to Old English swǣr gloomy, Gothic swers esteemed

Synonym Study

See earnest ¹.

Example Sentences

In practice, this means that suspects being charged with serious crimes today may not have a trial until late 2029 or early 2030.

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She was unable to drive at all for 12 years after a serious injury, which led to life-threatening sepsis and the amputation of her leg.

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He was, however, one of the few bright lights for Liverpool against Forest, the only player posing a serious threat, although he faded.

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This has serious repercussions for queer and trans actors, as well as the public.

Read more on Los Angeles Times

The latest figures come after the EA gave England's water companies their worst ever combined marks last month for their environmental performance in 2024, amid a spike in serious pollution incidents.

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Related Words

• dangerous 
• deep 
• difficult 
• far-reaching 
• grievous 
• important 
• major 
• meaningful 
• severe 
• significant 
• tough 
• urgent