illness既是可数名词，又是不可数名词。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。
His illness diminished his health.疾病侵蚀了他的健康。
He will pull through his illness soon.他很快就会恢复健康的。
Worry and illness had made him prematurely old.他心事重重、疾病缠身，落得个未老先衰。
His illness is owing to excessive work.
1、Attitudes to mental illness have shifted in recent years.
2、He boasts of dodging military service by feigning illness.
3、She was determined not to let the illness take hold again.