assiduous

American  

[uh-sij-oo-uhs] / əˈsɪdʒ u əs /

adjective

1. constant in application or effort; working diligently at a task; persevering; industrious; meticulous.

   an assiduous student.

   Synonyms:

   sedulous, diligent, studious

   Antonyms:

   lazy, inconstant

2. constant; unremitting.

   assiduous reading.

   Synonyms:

   persistent, tireless, continuous

   Antonyms:

   lazy, inconstant

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assiduous British  

/ əˈsɪdjʊəs /

adjective

1. hard-working; persevering

   an assiduous researcher

2. undertaken with perseverance and care

   assiduous editing

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Other Word Forms

• assiduously adverb
• assiduousness noun
• unassiduous adjective
• unassiduousness noun

Etymology

Origin of assiduous

First recorded in 1530–40; from Latin assiduus, equivalent to assid(ēre) “to sit near or beside, dwell close to” ( assess ) + -uus adjective suffix; -ous

Example Sentences

While he is destined to become the supreme governor of the Church of England, he isn’t an assiduous churchgoer.

From The Wall Street Journal • Mar. 11, 2026

Powell’s assiduous outreach to his colleagues gives him a good overview of where the proverbial bodies are buried, giving colleagues ample time to voice their objections.

From Barron's • Dec. 12, 2025

But saying no would have been difficult too, after months of assiduous effort put into developing a good relationship with President Trump.

From BBC • Jun. 22, 2025

A top-notch campus alone does not produce academic achievement — and, conversely, a brilliant teacher and an assiduous student in a one-room schoolhouse can make for an upstanding education.

From Los Angeles Times • May 23, 2025

Columbus had been an itinerant peddler of old maps and an assiduous reader of the books by and about the ancient geographers, including Eratosthenes, Strabo and Ptolemy.

From "Cosmos" by Carl Sagan

Related Words

• diligent
• exacting
• indefatigable
• laborious
• scrupulous
• zealous