What is a Function?

My definition for function: each input will be given an output or answer

The internet's definition: A rule that relates two variables, typically x and y,  is called a function  if to each value of x the rule assigns one and only one value of y. When that is the case, we say that y is a function of x.

Miss V's definition: f(x)=a

Every function is given a separate equation and a different answer.

The x-values is defined as the domain, while the y-values is the range.

If fraction is given as the answer while a zero is the denominator, it considered undefined.

Also if the a negative number cannot be within a radical sign/square root as a negative number is not part of a range.