形容詞 arduous:

1. characterized by toilsome effort to the point of exhaustion; especially physical effort
   同義詞：backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsome
2. taxing to the utmost; testing powers of endurance- F.D.Roosevelt
   同義詞：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.
   有關(guān)削減核武器的談判是一項(xiàng)漫長(zhǎng)而艱苦的工作
2. He mastered these words through the arduous consultation of the dictionary.
   通過(guò)勤查字典，他掌握了這些單詞。
3. Although the work was arduous, he finished it in a short time.
   雖然這項(xiàng)工作很費(fèi)力，他仍然很快就做完了。
4. It's an arduous task.
   這是一項(xiàng)艱巨的任務(wù)。

ar.du.ous

adj.（形容詞）
Demanding great effort or labor; difficult:
艱巨的：需要很大努力或工作的；困難的：
例句：
.the arduous work of preparing a Dictionary of the English Language.(Macaulay)
.制作一本英語(yǔ)語(yǔ)言詞典的艱巨工作.(麥考利)

Testing severely the powers of endurance; strenuous:
艱難的：忍耐力的嚴(yán)格考驗(yàn)的；艱苦的：
例句：
a long, arduous, and exhausting war.
一次長(zhǎng)期、艱難而疲憊不堪的戰(zhàn)爭(zhēng)

Hard to traverse, climb, or surmount.See Synonyms at burdensome ,hard
難攀登的，陡峭的：難以通過(guò)、攀登或克服的參見(jiàn) burdensome,hard

來(lái)源：
From Latin arduus [high, steep]
源自 拉丁語(yǔ) arduus [高的，陡峭的]

【引伸】
ar.duously
adv.（副詞）
ar.duousness
n.（名詞）