In mathematics, "undefined" refers to a situation where a value cannot be determined or does not have a meaningful interpretation. A common example is division by zero, such as in the expression 5 ÷ 0. Since there is no number that, when multiplied by zero, gives a non-zero number, this operation is considered undefined. In programming, "undefined" often indicates that a variable has been declared but has not been assigned a value. For instance, in the JavaScript programming language, if a variable is created without an initial value, it is automatically set to undefined. This helps developers identify uninitialized variables in their code.