An invertible function is a type of function that has a unique output for every input, allowing it to be reversed. This means that if you apply the function to a value and then apply its inverse, you will return to the original value. Mathematically, if f(x) is an invertible function, there exists an inverse function f^-1(x) such that f(f^-1(x)) = x . For a function to be invertible, it must be one-to-one (bijective), meaning no two different inputs produce the same output. Common examples of invertible functions include linear functions like f(x) = 2x + 3 and exponential functions like f(x) = e^x . In contrast, functions like f(x) = x^2 are not invertible because they produce the same output for different inputs.