# What does the long curly line mean?

Sorry to sound incredibly ignorant, but I am...at least in math anyway. What does this symbol: $\int$ mean?

-
You might want to look through wiki article on integration. – Sasha Sep 6 '11 at 0:24
There's no need to be so apologetic. We're all here to learn. – Austin Mohr Sep 6 '11 at 0:41
It is a double ended fishing pole – The Silence of the Cows Jun 3 '15 at 3:46

## 2 Answers

This is the symbol for integration. You may have seen it in Calculus. For example, $$\int x \, dx = \frac{1}{2}x^2 + C$$

-
Can you give me an example (simple please!) – david Sep 6 '11 at 0:23
Until you study Calculus, I don't know how much I can really say about the mathematics. I can give you an example of its practical use, however. Suppose you run a business and had a function that told your profit at any moment in time. The integral can be used to determine your total profit over an interval of time, such as over the course of an entire year. – Austin Mohr Sep 6 '11 at 0:31
Or rate of profit, anyway. – anon Sep 6 '11 at 0:47
@david: "I'm still in basic Geometry" - in that case, what book were you reading when you saw this? But Austin's right, you'll have to wait for calculus to appreciate this properly. – J. M. Sep 6 '11 at 1:16
@david, since you mention geometry, integrals can be used to compute the areas and volumes of complicated objects. The equation given by Austin says that the area of the isosceles right triangle having a side $x$ is $x^2/2$, but you probably knew that already. What you may not know is that the area of a parabolic sector is 2/3 the area of the parallelogram containing it and this is essentially given by the integral $\int x^2 = x^3/3$. – lhf Sep 6 '11 at 2:25

It is the symbol for the Integral; it is a stylized 'S' because the concept of the integral is a related to the Sum, which starts with S. (the mathematical symbol for Sum is a capital sigma, ∑ -- which is S in the traditional Grek alphabet from which mathematics borrows so many symbols.)

-