[L. fermentatio.] The sensible internal motion of the constituent particles of animal and vegetable substances, occasioned by a certain degree of heat and moisture, and accompanied by an extrication of gas and heat. Fermentation is followed by a change of properties in the substances fermented, arising from new combinations of their principles. It may be defined, in its most general sense, any spontaneous change which takes place in animal or vegetable substances, after life has ceased. It is of three kinds, vinous, acetous, and putrefactive. The term is also applied to other processes, as the panary fermentation, or the raising of bread; but it is limited, by some authors, to the vinous and acetous fermentations, which terminate in the production of alcohol or vinegar. Fermentation differs from effervescence. The former is confined to animal and vegetable substances; the latter is applicable to mineral substances. The former is spontaneous; the latter produced by the mixture of bodies.