See more synonyms for serious on
  1. of, showing, or characterized by deep thought.
  2. of grave or somber disposition, character, or manner: a serious occasion; a serious man.
  3. being in earnest; sincere; not trifling: His interest was serious.
  4. requiring thought, concentration, or application: serious reading; a serious task.
  5. weighty or important: a serious book; Marriage is a serious matter.
  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.
  1. that which is of importance, grave, critical, or somber: You have to learn to separate the serious from the frivolous.

Origin of serious

1400–50; late Middle English < Latin sērius or Late Latin sēriōsus; see -ous, -ose1
Related formsse·ri·ous·ness, nounhalf-se·ri·ous, adjectivehalf-se·ri·ous·ly, adverbhalf-se·ri·ous·ness, nounnon·se·ri·ous, adjectivenon·se·ri·ous·ly, adverbnon·se·ri·ous·ness, nouno·ver·se·ri·ous, adjectiveo·ver·se·ri·ous·ly, adverbo·ver·se·ri·ous·ness, nounqua·si-se·ri·ous, adjectivequa·si-se·ri·ous·ly, adverbsu·per·se·ri·ous, adjectivesu·per·se·ri·ous·ly, adverbsu·per·se·ri·ous·ness, nounul·tra·se·ri·ous, adjectiveul·tra·se·ri·ous·ly, adverbul·tra·se·ri·ous·ness, nounun·se·ri·ous, adjectiveun·se·ri·ous·ly, adverbun·se·ri·ous·ness, noun

Synonyms for serious

See more synonyms for on
2. sober, sedate, staid. 3. See earnest1. 5. momentous, grave.

Antonyms for serious

3, 5. trivial. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for nonserious


  1. grave in nature or disposition; thoughtfula serious person
  2. marked by deep feeling; in earnest; sincereis he serious or joking?
  3. concerned with important mattersa serious conversation
  4. requiring effort or concentrationa serious book
  5. giving rise to fear or anxiety; criticala serious illness
  6. informal worthy of regard because of substantial quantity or qualityserious money; serious wine
  7. informal extreme or remarkablea serious haircut
Derived Formsseriousness, noun

Word Origin for serious

C15: from Late Latin sēriōsus, from Latin sērius; probably related to Old English swǣr gloomy, Gothic swers esteemed
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for nonserious



mid-15c., "expressing earnest purpose or thought" (of persons), from Middle French sérieux "grave, earnest" (14c.), from Late Latin seriosus, from Latin serius "weighty, important, grave," probably from a PIE root *swer- (4) "heavy" (cf. Lithuanian sveriu "to weigh, lift," svarus "heavy;" Old English swære "heavy," German schwer "heavy," Gothic swers "honored, esteemed," literally "weighty"). As opposite of jesting, from 1712; as opposite of light (of music, theater, etc.), from 1762. Meaning "attended with danger" is from 1800.

Online Etymology Dictionary, © 2010 Douglas Harper

nonserious in Medicine


  1. Being of such import as to cause anxiety, as of a physical condition.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.