What is µ A below ~ x in the Fuzzy Logic
Here μ A˜(∙) μA~(∙) membership function of A˜ this assumes values in the range from 0 to 1, i.e.,  μ A ˜ (∙)∈[0,1] μA~(∙)∈[0,1] . The membership function  μ A ˜ 
(∙)  μA~(∙) maps   U to the membership space M . The dot  (∙) in the membership function described above, represents the element in a fuzzy set; whether it is discrete or continuous. 

In classical set theory, it is either 1 or 0. 

source:

https://www.tutorialspoint.com/fuzzy_logic/fuzzy_logic_membership_function.htm