What is arduous requires more energy and endurance, and is less within the reach of common powers, than what is hard. Its primitive meaning of steep climbing is still felt in it, and makes it suggestive of severe and protracted effort. [Century Dictionary]
arduous 需要更多的能量和耐力,不像 hard 那樣容易達到。它原始的攀爬意義仍然存在,並使其暗示了嚴峻而持久的努力。[世紀詞典]