The word "contagious" refers to something that can be easily spread or transmitted from one person or organism to another, especially in the context of diseases. For example, if a person has a contagious illness, it means that they can pass this illness to others through direct contact, air, or other means. The term can also be used metaphorically to describe behaviors or emotions that can be easily shared among people.
The word "contagious" comes from the Latin word "contagiosus," meaning "touching or contagious." This, in turn, comes from "contagium," which means "contact" or "infection," derived from "contingere," meaning "to touch."