n. (pl. calculuses or calculi) 1 Math. a a particular method of calculation or reasoning (calculus of probabilities). b the infinitesimal calculuses of integration or differentiation (see integral calculus, differential calculus). 2 Med. a stone or concretion of minerals formed within the body. calculous adj. (in sense 2).
[ L, = small stone used in reckoning on an abacus ]