Final answer:
Communicable diseases are infectious diseases that can be spread from one person to another, with pathogens as the causative agents. Contagious diseases are a type of communicable disease that are easily transmitted, such as measles through respiratory droplets.
Step-by-step explanation:
The term communicable refers to infectious diseases that can be transmitted or spread from one person to another. These diseases are caused by pathogens such as bacteria, viruses, fungi, parasites, and prions. They can be spread through direct contact with an infected person or through indirect mechanisms such as touching contaminated surfaces or breathing in infected droplets that enter the air when a sick person coughs or sneezes.
Contagious diseases are a subset of communicable diseases that are known to spread very easily from person to person. The level of contagiousness often depends on how the pathogen is transmitted. For instance, measles is a highly contagious disease transmitted through respiratory droplets, making it one of the most easily spread communicable diseases.