illness用法

illness 是可数的。。双数是illnesses..不过一般很少用

例如说像SARS， 就属于major illnesses。。illnesses 一般是指传染病

illness就比较单纯，比如说谁谁谁suffer from illness

名词 n.
1.
患病(状态);身体不适[U]
During his illness, John stayed indoors.
约翰在生病期间足不出户。
2.
(某种)疾病[C]
I have never seen her since her father fell sick of a serious illness.
自从她父亲生重病后,我就再也没有见过她。

llness往往指病人内部的虚弱或失调所致，故着眼点是内因。illness一般是一段时间或更长时间的不适，还可指一切心理的病症，从轻微神经病到严重的精神病，均可称之为illness.

illness是指病的状态，即由生病而引起的sickness。不是指一种病或几种病。所以是不可数名词。
见其字典释意：
illness is Poor health resulting from disease of body or mind; sickness.
A disease.