A function in math means a correspondence from one value x of the first set to another value y of the second set. This correspondence can be of the following four types. But every correspondence is not a function.
In the example below, only 1 – 1 and many to one are examples of a function because no two ordered pairs have the same first component and all elements of the first set are linked in them. So we say that in a function one input can result in only one output. If we are given any x then there is one and only one y that can be paired with that x. A function cannot be associated with two outputs. A curve drawn in a graph is represented as a function, then every vertical line intersects the curve in at most one point. This vertical line test helps us in determining whether the curve is a function or not.
