Pythagorean fuzzy set: state of the art and future directions

Pythagorean fuzzy set, generalized by Yager, is a new tool to deal with vagueness considering the membership grade mu and non-membership nu satisfying the condition mu 2+nu 2 <= 1. It can be used to characterize the uncertain information more sufficiently and accurately than intuitionistic fuzzy set. Pythagorean fuzzy set has attracted great attention of many scholars that have been extended to new types and these extensions have been used in many areas such as decision making, aggregation operators, and information measures. Because of such a growth, we present an overview on Pythagorean fuzzy set with aim of offering a clear perspective on the different concepts, tools and trends related to their extension. In particular, we provide two novel algorithms in decision making problems under Pythagorean fuzzy environment. It may be served as a foundation for developing more algorithms in decision making.