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adjective as·sid·u·ous \ə-ˈsij-wəs, -ˈsi-jə-\

Simple Definition of assiduous

  • : showing great care, attention, and effort

Source: Merriam-Webster's Learner's Dictionary

Full Definition of assiduous

  1. :  marked by careful unremitting attention or persistent application <an assiduous book collector> <tended her garden with assiduous attention>

assiduously adverb
assiduousness noun

Examples of assiduous in a sentence

  1. They were assiduous in their search for all the latest facts and figures.

  2. The project required some assiduous planning.

The history of assiduous

Assiduous came to English directly from the Latin assiduus, an adjective derived from the verb assidēre "to sit beside." To the ancient Romans, assiduus carried meanings ranging from “settled or rooted in place” to “constantly present” to “persistent, unremitting." This last sense was the one borrowed into English four hundred years ago and still used today, often in complimentary phrases such as "an assiduous student" and “assiduous efforts.” In the 18th century, the word took on a mildly pejorative meaning, "obsequious," when used of someone striving to please. This sense has largely passed out of use.

Did You Know?

Judges presiding over assizes (former periodical sessions of the superior courts in English counties) had to be assiduous in assessing how to best address their cases. Not only were their efforts invaluable, but they also served as a fine demonstration of the etymologies of "assiduous," "assess," and "assize." All three of those words derive from the Latin verb assidēre, which is variously translated as "to sit beside," "to take care of," or "to assist in the office of a judge." "Assidēre," in turn, is a composite of the prefix ad- (in this case, meaning "near" or "adjacent to") and sedēre, meaning "to sit."

Origin of assiduous

Latin assiduus, from assidēre

First Known Use: 1622

Synonym Discussion of assiduous

busy, industrious, diligent, assiduous, sedulous mean actively engaged or occupied. busy chiefly stresses activity as opposed to idleness or leisure <too busy to spend time with the children>. industrious implies characteristic or habitual devotion to work <industrious employees>. diligent suggests earnest application to some specific object or pursuit <very diligent in her pursuit of a degree>. assiduous stresses careful and unremitting application <assiduous practice>. sedulous implies painstaking and persevering application <a sedulous investigation of the murder>.

ASSIDUOUS Defined for Kids


adjective as·sid·u·ous \ə-ˈsi-jə-wəs\

Definition of assiduous for Students

  1. :  showing great care, attention, and effort <They were assiduous in gathering evidence.>

assiduously adverb

Seen and Heard

What made you want to look up assiduous? Please tell us where you read or heard it (including the quote, if possible).


the range of perception or understanding

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