sickness：較口語(yǔ)化，可與illness換用，但還可表示"惡心"。
disease ： 指具體的疾病，且通常較嚴(yán)重，發(fā)病時(shí)間也較長(zhǎng)。
complaint ： 現(xiàn)代英語(yǔ)中，既可指癥狀，也可指疾病。
例句：
1. Attitudes to mental illness have shifted in recent years.
最近幾年對(duì)精神病的態(tài)度已有所改變。
2. He boasts of dodging military service by feigning illness.
他炫耀自己通過(guò)裝病來(lái)逃避服兵役。
3. She was determined not to let the illness take hold again.
她決心不讓疾病再次擊垮自己。
4. Although her illness is serious, her condition is beginning to stabilize.
雖然她病得很重，但病情正開(kāi)始趨于穩(wěn)定。
5. The illness had a profound effect on his outlook.
這場(chǎng)病對(duì)他的人生觀產(chǎn)生了深刻的影響。