Which type of parasite lives on the outside of its host?

An ectoparasite is defined as a type of parasite that lives on the external surface of its host. These organisms attach themselves to the outside body of their host, obtaining nutrients and sometimes even protection while inflicting harm. Common examples of ectoparasites include ticks, lice, and fleas.

This contrasts with endoparasites, which reside within the host's body, in organs or tissues, and are typically not visible from the outside. Infestation refers to a condition where a host is populated by ectoparasites but does not specify the type of organism involved. Pathogens, while they can cause disease, are a broader category that includes bacteria, viruses, fungi, and other microorganisms that may or may not be parasitic in nature. In summary, ectoparasites are specifically characterized by their external relationship with the host, making them distinct from these other categories.