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Calculus is a generic term referring to any form of mathematics which has axioms and at least one fundamental theory. Some examples of mathematics that can be categorized as calculus are: algebra, geometry, arithmetic, etc.

Due to corruption of the definition over time, in modern usage "calculus" almost exclusively refers to "The Calculus." The Calculus is also known as "Newton's Calculus," or "Leibniz’s Calculus" depending on who you ask. Mathematics majors tend to refer to The Calculus as "Leibniz’s Calculus" and physics majors tend to refer to The Calculus as "Newton's Calculus.”
Any Given Major: "I need help with my calculus homework."
Physics Major: "Are you referring to 'Newton's Calculus?'"
Math Major: "I think you mean 'Leibniz's Calculus'"
Physics Major: “No, I mean ‘Newton’s Calculus,’ because Newton slapped Leibniz around like a step-child at Wal*Mart.”
Math Major: sob sob
by Andrew April 04, 2005
Calculus, which was discovered by Newton and Liebniz, nothwithstanding all credit being given to Newton, is one of the most beautiful forms of intellectual material. Calculus requires and emphasizes the development of new methods of thinking, and therefore it is not for the weak minded. Calculus has many practical applications including molecular and ecological biology, physics, engineering, social and political sciences, and business. After completing a very involved and thought-provoking problem involving differential equations or integrals, one might feel a certain "high."
Dude 1: "Yo man I got some bomb-ass shit that will fuck you up. Let's go blaze."
Dude 2: "Nah dude I got this problem for calc homework that involves differential equations and slope fields, and if I figure it out, my high will be stronger than the high off the strongest chronic"
by nirvanarageatm December 17, 2004
The one reason to allow Starbucks to take over the world.
"I have CALCULUS first hour?! Someone give me a fucking latte..."
by kissinclosets September 04, 2005
Calculus is how we know everything about everything, except sex, maybe.

It is also a name for the page and a half of indecipherable foreplay used in university physics textbooks before they give you the formula for something.
Engineering student: I forgot the formula for the volume of a sphere, but I was able to figure it out from the area of a circle using calculus.
Non-engineering student: I looked in the back of the textbook.
by Nick Bentzen April 11, 2008
"Hey, in our Calculus homework, why does the derivative of x^2 = 2x?"
by MikeWatch February 09, 2009
Calculus is a branch of mathematics, developed independently by Newton and Leibniz and formalized in the 19th century by various mathematicians, that revolutionized human understanding of the world. Mathematically, it allows us to talk about instantaneous rates of change and areas under arbitrary curves. Doesn't sound important? When does anyone use this? Differential equations, which express the relation between two quantities in terms of how they change with respect to one another, allow us to model situations in which we cannot explicitly find the relationship between quantities. This concept can be applied to model situations in physics, engineering, chemistry (how does this reaction progress?), physiology (how does a muscle contract?)...just about any science, as well as economics, sociology (how do new ideas spread?), and more. If you want to understand the world today, you need to understand calculus. Statistics too...but that's another story.

Calculus is not some super-hard subject that only the most brilliant can handle. If you have a good teacher who explains things precisely, you can learn calculus. (Finding such a teacher, unfortunately, can be the hard part.)
Guy 1: I have to go to calculus class now.
Guy 2: Calculus? That sucks.
Guy 1: No it doesn't. I'm finally learning math that I can apply -- you can't be an engineer without it!
by Daniel M May 03, 2006
Calculus is for anyone who ever complained that math isn't useful for anything. Calculus is a branch of mathematics that deals with problems involving changing rates. It has universal applications, finding its way into physics, engineering, medicine, economics, and anything that involves something changing. Calculus commands a great deal of notoreity from students learning it. But, like any form of mathematics, it is all pure logic, and if you understand it, it can be a very beautiful thing.
Newton and Leibniz both developed calculus on there own. Inventing calculus; now how fucking brilliant do you have to be to INVENT calculus? Pretty damn fucking brilliant.
by Fernando Martinez August 13, 2007
Usually the highest level of math taught at high schools. Must be taken by those considering to major in engineering, math or physics.

Otherwise, should still be taken to make transcript look better.
"I'm taking AP Calculus my senior year. I think it'll give me more options for college."
by AbnormalBoy April 19, 2004