Any organism capable of existing as either an autotroph or a heterotroph.

An autotroph refers to any organism that is capable of self-nourishment by using inorganic materials as a source of nutrients and using photosynthesis or chemosynthesis as a source of energy; such as, most plants and certain bacteria.

A heterotroph is an organism requiring organic compounds for its principal source of food or an organism that cannot manufacture its own food and instead obtains its nourishment and energy by taking in organic substances which is usually plant or animal matter.