This paper extends the notion of Pythagorean fuzzy sets and Fermatean fuzzy sets to 3, 4-
quasirung fuzzy sets (3, 4-QFSs). In 3, 4-QFSs, the sum of the cube of the membership
degree and fourth power of nonmembership degree is less than or equal to 1. Therefore, the
3, 4-QFSs can express imprecise information more flexibly and elaborately due to its
broader space. Here, we define the score function and accuracy function for the ranking of 3,
4-QFSs. Also, we develop complementary functions and some operational rules for the 3, 4 …