If a variable 'y' depends upon a variable 'x' in such a way that each value of 'x' determines exactly one value of 'y', then we say that

If a variable 'y' depends upon a variable 'x' in such a way that each value of 'x' determines exactly one value of 'y', then we say that

Explanation

 If each value of 'x' determines exactly one value of 'y', then:


The variable y depends on x


For every input x, there is a unique output y


This is the definition of a function in mathematics.