A mathematical expression which has no meaning and which cannot be interpreted is known mathematically as 'undefined.' The best example, is dividing a real number by 0. For instance, let us divide 8 by 2. The answer obviously is 4. However if we divide 8 by 0, there is no answer for the simple reason that there is no number. We all know that 0 times any real number gives you 0 and not 8. This simply means that division by 0 is undefined; it is incompatible with division by any other number.

For better understanding, you can go to the calculator on your computer by clicking on Start-Run-Calc. Divide any number by 0 and you will get an answer which is not a number but a sentence; try it! Simply put, something which has no meaning in the world of math is said to be undefined.

For better understanding, you can go to the calculator on your computer by clicking on Start-Run-Calc. Divide any number by 0 and you will get an answer which is not a number but a sentence; try it! Simply put, something which has no meaning in the world of math is said to be undefined.