Synonyms for Diligent (same or very similar meaning)
WordNet sense 1 (quietly and steadily persevering especially in detail or exactness):
persevering
WordNet sense 2 (enduring trying circumstances with even temper or characterized by such endurance):
patient
WordNet sense 3 (characterized by hard work and perseverance):
industrious, tireless
WordNet sense 4 (marked by care and persistent effort):
assiduous, sedulous
From the ODE community, based on WordNet
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