Â© 2013 WebMD, LLC. All rights reserved. The teeth are the hardest substances in the human body. Besides being essential for chewing, the teeth play an important role in speech. Parts of the teeth include: â¢ Enamel: The hardest, white outer part of the tooth. Enamel is mostly made of calcium phosphate, a rock-hard mineral. â¢ Dentin: A layer underlying the enamel.
While they are often used synonymously, the terms infectious disease and communicable disease do not have the same meaning. A communicable disease is an infectious disease that is easily spread from one human to another.
Two of the most commonly used words in classifying disease are contagious disease and infectious disease. Let us differentiate one word from the other. Infectious disease is said to be the mother word of the terms such as contagious disease, communicable disease, and transmissible disease. Generally, infectious diseases are defined as the ability of a disease to enter a host, transmit the disease, and infect that person. An infectious disease can be sub-classified as contagious or non-contagious.