Calculus :  (noun)
1: a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body; "renal calculi can be very painful" [syn: concretion]
2: an incrustation that forms on the teeth and gums [syn: tartar, tophus]
3: the branch of mathematics that is concerned with limits and with the differentiation and integration of functions [syn: the calculus, infinitesimal calculus]