A variable of integration is the variable with respect to which an integral is computed. It is typically represented as 'dx' in the integral notation.
variable of integration cheat sheet for homework
Integrand: The function that is being integrated in an integral.
Definite Integral: $\int_{a}^{b} f(x) \, dx$ represents the area under $f(x)$ from $x=a$ to $x=b$.
Indefinite Integral: $\int f(x) \, dx$ represents a family of functions differing by a constant.