Abstract
Handling vagueness of verbal meanings and discreteness of word is very important to use verbal expressions in the field of engineering and so on. The former can be expressed by using fuzzy sets adequately, while suitable method to handle the latter has not been found yet. This paper aims to give the definition of the fuzzy set which expresses between one fuzzy set and the other in order to handle the discreteness. It is called "Between Set". After explaining mathematical conditions of support set and two original fuzzy sets and practical meanings of them, the membership function of between set is defined as the value subtracted absolute difference of membership values between two fuzzy sets from unity. It is described that between set has splendid characteristics as convexity, high performance to express elements and so on. Advantages of it are demonstrated in comparison it with the other sets calculated by another operators.
