1. hard => arduous (由于英语受到法语的影响加h或h脱落其含义不变，主要是因为法语中的h不送气也就是不发音。例如：arc => arch-).
2. ortho- => orthodox => arduous.
3. orthodox => arduous.
4. Literal sense of "high, steep, difficult to climb".
arduous:  Latin arduus, the source of English arduous, originally meant ‘high, steep’ (it is related to Greek orthós ‘straight, upright, correct’, as in English orthodox); the sense ‘difficult, laborious’ was a later metaphorical development. (The word has no connection with ardour, which comes ultimately from Latin ardēre ‘burn’; see ARSON.)
- arduous (adj.)
- 1530s, "hard to accomplish, difficult to do," from Latin arduus "high, steep," also figuratively, "difficult," from PIE root *eredh- "to grow, high" (see ortho-). Literal sense of "high, steep, difficult to climb," attested in English from 1709.
- 1. an arduous journey across the Andes
- 2. Take your ease, for the journey ahead will be long and arduous.
- 好好休息一下, 前面的路程远而艰难呢.
- 3. The refugees made an arduous journey through the mountains.
- 4. The task is arduous; besides , there's not much time.
- 任务 艰巨, 同时时间又很紧迫.
- 5. We must have patience in doing arduous work.