What is an organism that can live both as a parasite and independently referred to as?

An organism that can live both as a parasite and independently is referred to as a facultative parasite. This term describes organisms that do not rely exclusively on a host for survival and can also thrive in an independent manner in a suitable environment. This adaptability allows facultative parasites to switch between a parasitic lifestyle, where they derive nutrients and benefit from a host, and a free-living existence, where they can obtain nutrients from their surroundings.

In contrast, obligate parasites are organisms that cannot complete their life cycle without exploiting a suitable host. They depend entirely on their host for survival and reproduction, making them incapable of living independently. Symbionts are organisms that live in close association with another species, often benefiting both parties, but this does not encompass the independent lifestyle aspect of facultative parasites. Endoparasites are those that live within the body of their host, which limits their ability to survive independently outside of a host environment. Thus, the definition of a facultative parasite accurately captures the essence of the organism's dual lifestyle.