The key to understanding the difference between communicable and non-communciable disease lies in the root of the these two words. The Latin word communis means "shared." Thus, communicable diseases are those which are able to be shared with another person, whereas non-communicable diseases are those which cannot be shared with another person.
Diseases like the flu, common colds, chicken pox, strep throat, and sexually transmitted diseases such as HIV/AIDS would be examples of a communicable disease.
Diseases like appendicitis, arthritis, cancer, diabetes, gingivitis, and Parkinson’s syndrome are examples of non-communicable diseases.
So, a person cannot get cancer from coming in contact with someone who has cancer, but a person can get the flu from coming into contact with someone who has it.