cal·cu·lus 
(kălkyə-ləs)
(kălkyə-ləs)n. pl. cal·cu·li (-lī′) or cal·cu·lus·es
1. Medicine An abnormal concretion in the body, usually formed of mineral salts and found in the gallbladder, kidney, or urinary bladder, for example.
2. Dentistry See tartar.
3. Mathematics
a. The branch of mathematics that deals with limits and the differentiation and integration of functions of one or more variables.
b. A method of analysis or calculation using a special symbolic notation.
c. The combined mathematics of differential calculus and integral calculus.
4. A system or method of calculation: "[a] dazzling grasp of the nation's byzantine budget calculus" (David M. Alpern).
[Latin, small stone used in reckoning; see CALCULATE.]