arduous

Compared meaning: needing a lot of effort (adjective).

比较义项：费力的（形容词）。

• hard

  The plain, all-purpose word for effort, physical or mental; neutral in tone and far more common in everyday speech than the other three.

  “费力的”最普通、最通用的说法，可指体力或脑力上的努力；语气中性，在日常口语中比另外三个词常见得多。

  This math problem is harder than I expected.

  这道数学题比我预想的要难。

• arduous 本词

  A formal word for a task, journey or process that demands great and often prolonged effort, usually in writing rather than casual speech.

  一个正式用词，指需要巨大且往往是长时间努力的任务、旅程或过程，多用于书面语而非日常口语。

  After an arduous three-day trek, the hikers finally reached base camp.

  经过三天费力的跋涉后，徒步者们终于到达了大本营。

• strenuous

  Focuses on physical exertion or energy used, and is the standard word in fitness or medical contexts, such as advice to avoid strenuous exercise.

  强调所耗费的体力或精力，是健身或医学语境中的标准用词，例如建议避免剧烈运动时常用此词。

  Doctors advised her to avoid strenuous exercise until her knee healed.

  医生建议她在膝盖痊愈之前避免剧烈运动。

• punishing

  Stresses the exhausting, harsh toll an activity takes on the body, often describing an extreme schedule, pace or climb rather than a single task.

  强调某项活动给身体带来的令人精疲力竭、严酷的消耗，常用来形容极端的日程、节奏或攀登，而不是单一的任务。

  The team endured a punishing schedule of five games in six days.

  这支队伍忍受了六天内打五场比赛的高强度消耗赛程。

All four mean needing much effort. Hard is plain and common. Arduous is formal, for long, demanding tasks or journeys. Strenuous means physical effort, common in fitness contexts. Punishing means an exhausting toll on the body, like a harsh schedule. Other senses are not compared.

这几个词在“费力的”这一义项上意思相近，但正式程度和适用范围不同：hard最口语化、最通用，脑力体力皆可用；arduous多用于书面语，形容长时间或艰巨的任务和旅程；strenuous强调体力消耗，常见于运动或医学语境；punishing则强调活动对身体造成的极度疲惫感，常形容高强度的日程或节奏。这里不比较hard的其他常见义项（如“坚硬的”“严厉的”），也不比较punishing表示“惩罚性的”（如punishing tax）的义项。