illness既是可数名词，又是不可数名词。意为患病、身体不适时，是不可数的；意为某种疾病时，是可数的。Illness的读音为：英/?ln?s/、美/?ln?s/。
1.患病(状态)、身体不适[U]，此时不可数，例：During his illness,John stayed indoors.约翰在生病期间足不出户。
2.(某种)疾病[C]，此时可数。例：I have never seen her since her father fell sick of a illness.
