arduous

形容词 arduous:

1. characterized by toilsome effort to the point of exhaustion; especially physical effort
   同义词：backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsome
2. taxing to the utmost; testing powers of endurance- F.D.Roosevelt
   同义词：straining, strenuous
3. difficult to accomplish; demanding considerable mental effort and skill

1. Negotiating a reduction in nuclear arms is a long and arduous undertaking.
   有关削减核武器的谈判是一项漫长而艰苦的工作
2. He mastered these words through the arduous consultation of the dictionary.
   通过勤查字典，他掌握了这些单词。
3. Although the work was arduous, he finished it in a short time.
   虽然这项工作很费力，他仍然很快就做完了。
4. It's an arduous task.
   这是一项艰巨的任务。

ar.du.ous

adj.（形容词）
Demanding great effort or labor; difficult:
艰巨的：需要很大努力或工作的；困难的：
例句：
.the arduous work of preparing a Dictionary of the English Language.(Macaulay)
.制作一本英语语言词典的艰巨工作.(麦考利)

Testing severely the powers of endurance; strenuous:
艰难的：忍耐力的严格考验的；艰苦的：
例句：
a long, arduous, and exhausting war.
一次长期、艰难而疲惫不堪的战争

Hard to traverse, climb, or surmount.See Synonyms at burdensome ,hard
难攀登的，陡峭的：难以通过、攀登或克服的参见 burdensome,hard

来源：
From Latin arduus [high, steep]
源自 拉丁语 arduus [高的，陡峭的]

【引伸】
ar.duously
adv.（副词）
ar.duousness
n.（名词）