Fatigue vs Lethargy - What's the difference?

fatigue | lethargy |

As nouns the difference between fatigue and lethargy

is that fatigue is a weariness caused by exertion; exhaustion while lethargy is (pathology) a condition characterised by extreme fatigue or drowsiness, or prolonged sleep patterns.

As a verb fatigue

is to tire or make weary by physical or mental exertion.




(en noun)
  • A weariness caused by exertion; exhaustion.
  • * {{quote-news
  • , year=2012 , date=December 29 , author=Paul Doyle , title=Arsenal's Theo Walcott hits hat-trick in thrilling victory over Newcastle , work=The Guardian citation , page= , passage=Alan Pardew finished by far the most frustrated man at the Emirates, blaming fatigue for the fact that Arsenal were able to kill his team off in the dying minutes.}}
  • A menial task, especially in the military.
  • (engineering) A mechanism of material failure involving of crack growth caused by low-stress cyclic loading.
  • * 2013 , N. Dowling, Mechanical Behaviour of Materials , page 399
  • Mechanical failures due to fatigue have been the subject of engineering efforts for more than 150 years.



    Derived terms

    * fatigues (military work clothing)


  • to tire or make weary by physical or mental exertion
  • to lose so much strength or energy that one becomes tired, weary, feeble or exhausted
  • (intransitive, engineering, of a material specimen) to undergo the process of fatigue; to fail as a result of fatigue.
  • lethargy



  • (pathology) A condition characterized by extreme fatigue or drowsiness, or prolonged sleep patterns.
  • * c. 1599 , (William Shakespeare), King Henry IV, Part 2 :
  • This Apoplexie is (as I take it) a kind of Lethargie , a sleeping of the blood, a horson Tingling.
  • * 2003 , Amanda Ripley, "At Last, the Pill for Men", Time , 20 Oct 2003:
  • So in order to avoid unpleasant side effects like lethargy and sexual dysfunction, most recent trials also gave men testosterone supplements.
  • A state of extreme torpor or apathy, especially with lack of emotion or interest; loosely, sluggishness, laziness.
  • * Atterbury
  • Europe lay then under a deep lethargy .
  • * 1995 , Bruce W Nelan, "Crime and Punishment", Time , 20 Mar 1995:
  • Yakovlev, one of the architects of the reforms put in place by Mikhail Gorbachev, says he too is "amazed" at the government's lethargy .
  • * 2008 , Nick Fletcher, The Guardian , 9 May 2008:
  • The increase in mining stocks helped the FTSE 100 shake off some earlier lethargy and close 9.8 points higher at 6270.8, despite the disappointment of unchanged UK interest rates.