A disease is a kind of sickness. If a disease is contagious, you can get that type of sickness from other people. Not all types of disease are contagious. Some diseases are common and not life-threatening, but other diseases are very serious and can kill you.
Cancer is a disease that affects millions of people.
Elderly people might get Alzheimer’s disease. It’s not a contagious disease.
A virus that causes a disease is infectious. (You can get from other people.)
AIDS is a disease that develops from the HIV virus.
The measles is a contagious disease.
Ebola is a very dangerous disease. You can catch it from other people.
Tuberculosis is a common disease in some third world countries.
Malaria is a disease spread by mosquitoes.
Cardiovascular disease is not infectious. (This is a disease that affects your heart.)
It’s important to pay attention to reports of any new diseases.
To help prevent the spread of a disease, you should always wash your hands.
Brush and floss your teeth to prevent gum disease.
He’s dying from an incurable disease.
The word "diseased" is an adjective:
I have a diseased tree in my front yard. The tree has to come down.
If your kidneys are diseased, you might require dialysis treatments.
Richard is going to die because he has a diseased liver.