Definite Integral: The exact area under a curve between two points on a graph, often calculated using limits and represented as $\int_a^b f(x) dx$.
Subinterval: A smaller division within an interval used in numerical methods like Riemann sums to approximate integrals.
Trapezoidal Rule: A numerical method for approximating an integral by dividing the area under a curve into trapezoids rather than rectangles.