What defines a parasite?

A parasite is defined as an organism that benefits at the expense of its host. This definition highlights the relationship between the parasite and the host, where the parasite extracts nutrients or other benefits from the host organism, often to the detriment of the host's health or well-being. This relationship is a crucial aspect of various ecological systems and contributes to understanding interactions within those systems.

Parasites can take various forms, including protozoa, worms, and ectoparasites like fleas or ticks, and their existence often leads to significant health implications for the host. Understanding this definition helps in the study of parasitology and informs practices in environmental health, especially in relation to disease control and management.