Calculus (noun)

1. A branch of mathematics dealing with derivatives and integrals, and the study of how they relate to the behavior of functions.
2. A method of calculation or system of reasoning.
3. A tiny concretion or deposit, especially one in the body, such as a calculus in the gallbladder.

Origin:

From latin calculus, "small stone" (used for counting), from calcarius, "pertaining to lime or limestone", from calx, "lime".

Examples:

1. She was studying calculus in preparation for her engineering degree.
2. The calculation of the optimal solution for the problem required advanced calculus.
3. The new calculus method allowed for much more efficient computation.
4. The scientist developed a calculus to understand the behavior of fluids under pressure.
5. The patient had to undergo surgery to remove a calculus that was causing pain in her gallbladder.