assiduous

Universal Words adjective (formal) working very hard and taking great care that everything is done as well as it can be SYNDILIGENT: one of the most assiduous members of the team * their assiduous efforts and attention to detail * She was assiduous in her duties. assiduity noun [U] (rare) assiduously adverb: He worked assiduously to earn the money for his son's education.