The anatomy of Chinese characters: 疾病 矢 痛 痛苦

Once you recognize the important radical of sickness/illness (or anything pathological), you’ll learn many characters with ease.

疾病 means sickness/illness, each (疾 or 病) used separately, also means the same thing. 矢 means ‘arrow’.

痛 is pain or painful (like English, same character can be used as noun, verb, or adjective), 病痛 also means sickness/illness.

苦 means bitter or bitterness, so 痛苦 (painful bitterness) is ‘suffering’ or ‘affliction’.