Dividing a number by zero, such as in the expression 5 ÷ 0, is undefined in mathematics. This means that there is no number that can be multiplied by zero to give a non-zero number like 5. In simpler terms, you cannot split something into zero parts, as it doesn't make sense to have no parts at all. When we divide by a number, we are essentially asking how many times that number fits into another. Since 0 cannot fit into any number, division by zero leads to confusion and is not allowed in standard arithmetic.