Parasite

Definition
noun, plural: parasites
An organism that obtains nourishment and shelter on another organism
Supplement
Parasitism is s form of symbiosis in which one organism (called parasite) benefits at the expense of another organism usually of different species (called host). This host-parasite association may eventuate to the injury of the host.
Parasites can cause harm or disease to their host. They are generally much smaller than their hosts. Examples of parasites are tapeworms, flukes, lice, ticks, etc. Parasites may be classified into different categories. For instance, parasites may be macroparasites or microparasites based on their size. Macroparasites are those that are bigger in size and visible to an unaided eye. Microparasites are those that are small and can be detected through microscopy. Parasites may also be obligate or facultative depending on their interaction with their hosts. Obligate parasites are those that require a host to complete their life cycle. Facultative parasites are those that do not depend on a host to complete its life cycle. Certain parasites require only one host and they are referred to as direct parasites. Those that require both an intermediate host and a definitive host are called indirect parasites. Parasites that live outside the host are called ectoparasites whereas those that live inside the host are called endoparasites.
Word origin: Latin parasitus from Greek parasitos (person who eats at the table of another).
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