In mathematics, a domain refers to the set of all possible input values for a function. A function's domain can be restricted, meaning that not all values are allowed, or it can be unrestricted, meaning that all values are allowed.
Whether a value can be repeated in the domain of a function depends on the specific function and how it is defined. For example, a function that returns the square of its input will accept any real number as its input, and the same value can be used multiple times as an input to the function. On the other hand, a function that calculates the square root of its input will only accept non-negative real numbers, and the same value can only be used once as an input to the function.
In general, the domain of a function is determined by its definition and the restrictions imposed on its inputs. The domain of a function can be continuous, discrete, or a combination of both, and it can be finite or infinite.
