Applied to all petrologic units seen in microscopic sections of coal, as distinct from the visible units seen in the hand specimens. Comparable in rank to mineral as used in petrography. Thus, macerals are organic units composing the coal mass, being the 1865 descriptive equivalent of the inorganic units composing rock masses and universally called minerals. Individual macerals have the termination -inite; i.e., vitrinite, as the organic unit making up the lithologic specimen, vitrain. Three groups are recognized: (1) vitrinites; (2) exinites; and (3) inertinites.