What is the meaning of crisp in set?

A crisp set is a set whose characteristic function takes only two values, usually 0 and 1. In other words, each element of the set is either definitely in the set or definitely not in the set.

For example, the set of all even numbers is a crisp set. Each integer is either even or not even, and there is no ambiguity about which integers are in the set and which are not.

Contrast this with a fuzzy set, which is a set whose characteristic function can take values between 0 and 1. This allows for elements to be partially in the set and partially not in the set.

For example, the set of all tall people is a fuzzy set. There is no clear-cut definition of what it means to be tall, so some people may be considered tall while others are considered not tall.