(1) 在这些表示疾病或一段时间健康状况不佳的词中，sickness, illness最常用，常可互换。illness有时可指时间较长的病，而sickness指时间较短的病。

• That sickness kept him in bed for three weeks and left him weak for months afterwards.
  那次生病使他卧床了三周并在此后的数月内身体都很弱。
• He got an illness in his early years that didn't cause him much difficulty/trouble in his youth but began to take its toll as he reached middle age.
  他早年得过病，年轻时未引起多少麻烦，但随着人到中年却开始发起威来。
• I was laid up for six weeks with a very serious illness .
  我因一场重病躺了六周。
• Children are susceptible to various illnesses .
  儿童易患各种疾病。

 (2) ①sickness还作“恶心，呕吐”解。

• He felt a wave of sickness coming over him.
  他感到一阵恶心向他涌来。

②sickness可与其他词结合，构成复合词，如sea-sickness(晕船)，air-sickness(晕机)，mountain/altitude sickness(高山反应)等。

 (3) ①disease也是常用词，表示“疾病”，可指身体的、精神的，也可指植物病害；可以是通称，也可是具体某种疾病，与illness为同义词。illness多指患病状态，具体疾病多用disease。

• The business of doctors is to prevent and cure disease .
  医生的职责是预防和治疗疾病。
• Measles, mumps and influenza are common diseases .
  麻疹、腮腺炎和流感是常见疾病。
• Some skin diseases are difficult to treat. (不宜用illness或sickness)
  有些皮肤病是很难治疗的。
• The disease almost killed the apple trees in this region.
  这种病害把这个地区的苹果树几乎都给弄死了。

②disease有时用于引申意义。

• We must fight to get rid of poverty, ignorance, superstition and other social diseases .
  我们必须为消除贫穷、愚昧、迷信和其他社会弊病而战。

 (4) ailment指“疾病”，既可指轻症，也可指重病。

• His wife died of a brain ailment three years ago.
  三年前他的妻子死于脑病。
• He was suffering from a stomach/skin ailment .
  他深受胃病/皮肤病的折磨。
• I often suffer from trifling ailments .
  我常患些小病。

 (5) complaint也可表示“疾病，病痛”，还表示患者向医生诉说病情。

• He used to suffer from a heart complaint .
  他曾遭受心脏病的折磨。
• Arthritis is a complaint commonly found among the elderly.
  关节炎是老年人群中的一种常见疾病。
• He is a trainee helping the doctor to note the complaints of the patients.
  他是一名实习生，负责帮助医生记录患者的病情。

 (6) trouble可作“病痛，毛病”解，可泛指，如：back trouble (背痛), chest/kidney/heart/lung trouble等。

• I have been suffering from digestive troubles recently.
  近来我一直深受消化系统疾病的折磨。

 (7) indisposition指“身体不适，微恙”。

• He came to our party in spite of indisposition caused by a chill.
  尽管因为着凉身体不适，他还是赶来参加我们的宴会。

 (8) disorder可表示“(因身心机能紊乱、失调造成的)不适，疾病，毛病”。

• I suffered from a disorder of the digestive system last week.
  上周我因消化系统紊乱而深受其苦。
• Disorders of the mind are usually not easy to treat.
  精神紊乱通常不容易治愈。

 (9) infirmity作“虚弱，疾病”解时多用于书面语。

• Deafness and failing eyesight are among the infirmities of old age.
  耳聋眼花属于老年病。
• The infirmities left by an illness can be worse than the illness itself.
  疾病遗留下的身体虚弱可能比疾病本身更糟糕。