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[uh-sij-oo-uh s]
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  1. constant; unremitting: assiduous reading.
  2. constant in application or effort; working diligently at a task; persevering; industrious; attentive: an assiduous student.
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Origin of assiduous

1530–40; < Latin assiduus, equivalent to assid(ēre) to sit near, beside, dwell close to (see assess) + -uus deverbal adj. suffix; see -ous
Related formsas·sid·u·ous·ly, adverbas·sid·u·ous·ness, nounun·as·sid·u·ous, adjectiveun·as·sid·u·ous·ly, adverbun·as·sid·u·ous·ness, noun


See more synonyms for assiduous on Thesaurus.com
1. continuous, tireless, persistent. 2. studious, diligent, sedulous.


1, 2. inconstant, lazy.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for assiduous


  1. hard-working; perseveringan assiduous researcher
  2. undertaken with perseverance and careassiduous editing
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Derived Formsassiduously, adverbassiduousness, noun

Word Origin

C16: from Latin assiduus sitting down to (something), from assidēre to sit beside, from sedēre to sit
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 assiduous


1530s, from Latin assiduus "attending; continually present, incessant; busy; constant," from assidere "to sit down to," thus "constantly occupied" at one's work; from ad "to" (see ad-) + sedere "to sit" (see sedentary). The word acquired a taint of "servility" in 18c. Related: Assiduously; assiduousness.

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Online Etymology Dictionary, © 2010 Douglas Harper