illness ،Disease

Iّّّّّّّllness and disease are often used in the same way and are equally common in spoken English

However, illness is more often used to refer to the length of time or state of being unwell • He died after a long illness. • if you are off school because of illness

Do not use illness to talk about less serious problems such as headaches or colds.

Disease is a particular kind of illness, especially one that spreads from one person to another or affects a particular part of your body • infectious diseases • heart disease

Disease can also be used to mean a lot of different diseases • Cigarette smoking causes death and disease.