Primary purpose of this article is to Define and Discuss on Definite Integrals, in calculus point of view. The definite integral of a function is closely in connection with the anti derivative and indefinite integral of a function. The primary difference is that the indefinite integral, if that exists, is a authentic number value, while the latter two represent an infinite number of functions that differ only by way of a constant. The development in the definition of the definite integral begins having a function f( x), that is continuous on a closed interval (a, b).