Which of the following is a characteristic of a function?

A key characteristic of a function is that each input corresponds to exactly one output. This means that if you take any value from the domain (input), there will be a specific value in the range (output) associated with it. This relationship is crucial because it ensures that each element in the domain pairs with a unique element in the range, which is foundational to the definition of a function.

The idea that each input corresponds to at least one output highlights that functions can take an input and produce a direct output, even if the output is not unique. However, it is important to note that while some inputs can provide the same output—indicating that multiple inputs can indeed lead to the same output in a function—each individual input still cannot pair with more than one output.

Therefore, recognizing that each input must have a corresponding output solidifies the understanding of functions in algebra and higher mathematics, which is essential for problem-solving and graphical representation of functions.