In mathematics, it is possible for a domain to repeat in a function. This occurs when two or more distinct inputs produce the same output. When this happens, the function is not one-to-one, which means that it does not have a unique output for every input.
For example, consider the function f(x) = x^2. This function maps each input to its square. The domain of this function is all real numbers, since we can input any real number into the function. However, if we look at the outputs of the function, we notice that some outputs can be produced by more than one input. For instance, both 2 and -2 have the same square, which is 4. Therefore, the function f(x) = x^2 is not one-to-one and its domain repeats.
In the context of internet domains, however, domain names cannot repeat, as each domain name must be unique and registered only once. If a domain name is already registered, it cannot be used by another entity unless the original owner releases it or the domain expires and becomes available for registration again.
