Hai guys here comes the clear cut definition of function.
Consider the equation y = x – 3.
Here ‘x’ is called an independent variable (or input) and ‘y’ is called dependent variable ( or output).
The value of ‘y’ depends upon the the value of ‘x’
The word depends upon mathematically called FUNCTION.
Symbolically y = f(x) , the value of f at ‘x’