| arduous | (adjective) difficult to accomplish; demanding considerable mental effort and skill | - |
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| (adjective) characterized by effort to the point of exhaustion; especially physical effort | Synonyms: backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsome |
| (adjective) taxing to the utmost; testing powers of endurance | Synonyms: straining, strenuous |
| assiduous | (adjective) marked by care and persistent effort | Synonyms: sedulous |
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| deciduous | (adjective) (of plants and shrubs) shedding foliage at the end of the growing season | - |
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| (adjective) (of teeth, antlers, etc.) being shed at the end of a period of growth | - |
| duodecimal | (adjective) based on twelve | - |
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| duodenal | (adjective) in or relating to the duodenum | - |
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| gastroduodenal | (adjective) of or relating to the stomach and the duodenum | - |
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