## Well-defined

In mathematics, a function is **well-defined** if it gives the same result when the form (the way in which it is presented) but not the value of an input is changed. For example, a function that is well-defined will take the same value when 0.5 is the input as it does when 1/2 is the input. An example of a "function" that is not well-defined is "*f*(*x*) = the first digit that appears in *x*". For this function, *f*(0.5) = 0 but *f*(1/2) = 1. A "function" such as this would not be considered a function at all, since a function must have exactly one output for a given input.

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### More definitions of "well-defined":

- (
*adj*): Having a clean and distinct outline as if precisely cut along the edges.

Example:*"Well-defined features"*

Synonyms: chiseled