Division by zero occurs when a number is divided by zero, which is mathematically undefined. For example, if you try to divide 5 by 0, there is no number that can be multiplied by 0 to give 5. This creates a problem because division is essentially the inverse of multiplication. In mathematics, dividing by zero does not yield a meaningful result. It can lead to contradictions and inconsistencies in calculations. Therefore, mathematicians agree that division by zero is not allowed, and it is important to avoid this operation in any mathematical work.