What term is defined as an illness that can be contracted from another person?

The term defined as an illness that can be contracted from another person is "contagious disease." Contagious diseases are typically caused by infectious agents such as bacteria, viruses, or parasites and can spread through direct contact, respiratory droplets, or contaminated surfaces. Common examples include the flu, colds, and COVID-19. Understanding how these diseases spread is crucial for prevention and control measures.