Lower Sum:An approximation method where each rectangle's height is determined by the minimum function value over a subinterval, underestimating the area.
Riemann Sum:A method for approximating definite integrals by summing up areas of rectangles based on function values at specified points within subintervals.
Definite Integral:The exact area under a curve between two points on a graph, typically calculated using limits and Riemann sums.