It basically means that one variable is linked to another in a one-way (or possibly bijective) mapping. That is, if variable

is function of

, then choosing a value for

will yield a (or possibly more) value(s) for

by this particular mapping which actually is the function.

For instance, saying that

is function of

by the function

, we see that by choosing a value for

, we immediately obtain another value for

which is function of

via this function.

Does it make sense ?

I think I confused you more than helped you didn't I