Definition:Primitive (Calculus)

Definition
Let $F$ be a real function which is continuous on the closed interval $\left[{a .. b}\right]$ and differentiable on the open interval $\left({a .. b}\right)$.

Let $f$ be a real function which is continuous on the open interval $\left({a .. b}\right)$.

Suppose that:
 * $\forall x \in \left({a .. b}\right): F^{\prime} \left({x}\right) = f \left({x}\right)$.

Then $F$ is known as a primitive (or an antiderivative) of $f$.

Integration
The process of finding a primitive for a function is known as integration.

Arbitrary Constant
From the language in which it is couched, it is apparent that the primitive of a function may not be unique, otherwise we would be referring to $F$ as the primitive of $f$.

This point is made apparent in Primitives which Differ by a Constant: if a function has a primitive, there is an infinite number of them, all differing by a constant.

That is, if $F$ is a primitive for $f$, then so is $F + C$, where $C$ is a constant.

This constant is known as an arbitrary constant (or disposable constant - that is, it may be "disposed as desired", not "disposed of").

Indefinite Integral
From the Fundamental Theorem of Calculus, it is apparent that to find the value of a definite integral for a function between two points, one can find the value of the primitive of the function at those points and subtract one from the other.

Thus arises the notation $\displaystyle \int f \left({x}\right) dx = F \left({x}\right) + C$.

In this context, the expression $\displaystyle \int f \left({x}\right) dx$ is known as the indefinite integral of $f$.