WordReference Random House Learner's Dictionary of American English © 2015cal•cu•lus^{} */ˈkælkyələs/USA pronunciation*
n. [uncountable]
- Mathematicsa branch of mathematics that calculates amounts that change constantly:Calculus can help you figure out how fast an object falls.
- Dentistrya hard, yellowish substance on teeth formed from dental plaque;

tartar.

Collins Concise English Dictionary © HarperCollins Publishers::

**calculus** /ˈkælkjʊləs/ n ( pl -luses)- a branch of mathematics, developed independently by Newton and Leibniz. Both
**differential calculus** and **integral calculus** are concerned with the effect on a function of an infinitesimal change in the independent variable as it tends to zero - any mathematical system of calculation involving the use of symbols
- ( pl -li / -ˌlaɪ/) a stonelike concretion of minerals and salts found in ducts or hollow organs of the body

Etymology: 17th Century: from Latin: pebble, stone used in reckoning, from *calx* small stone, counter
'**calculus**' also found in these entries: