| strict(adjective, careful, thorough, meticulous, vigilant) | |
| strong-willed(adjective, resolute, tenacious) | |
| thoughtful(adjective, serious, reflective, vigilant) | |
| tough(adjective, difficult, careful, resolute, thorough) | |
| true(adjective, certain, careful, resolute, reliable) | |
| undaunted(adjective, tenacious) | |
| unremitting | |
| unwearied | |
| unyielding(adjective, resolute) | |
| working(adjective, lively, active, busy, occupied) | |
| academic(thoughtful, serious, reflective) | |
| aggressive(adjective, keen, intense, energetic, lively) | |
| agog | |
| aware | |
| bookish(thoughtful, serious, reflective) | |
| brisk | |
| bullheaded(adjective, resolute, tenacious) | |
| businesslike(adjective, activity, efficient, professional) | |
| bustling | |
| concerned(adjective, attentive) |
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| APA | Smart Define. (2015). diligent thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/diligent/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "diligent thesaurus" https://smartdefine.org/diligent/thesaurus/synonyms (accessed September 21, 2026). |
| Harvard | Smart Define 2015, diligent thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/diligent/thesaurus/synonyms>. |
| MLA | Smart Define. "diligent thesaurus" 14 April 2015. Web. 21 September 2026. <https://smartdefine.org/diligent/thesaurus/synonyms> |