aphthae Definition

a speck, flake, or blister on the mucous membranes (as in the mouth or gastrointestinal tract or on the lips) characteristic of some diseases (as thrush)

one of the vesicles filled with clear serous fluid that occur in the mouth, on the udder, and in the spaces between the digits of cloven-footed animals in some diseases —usually used in plural

a disease (as foot-and-mouth disease) characterized by aphthae