Centroid fuzzy entropy and weighted fuzzy entropy of type-2 fuzzy sets are studied, and their expressions are
constructed. For the special case of type-2 fuzzy sets, a new definition of fuzzy entropy of interval-valued fuzzy sets is
proposed, which remedies the shortcomings of existing ones in the cases that when an interval-valued fuzzy set degenerates
the ordinary fuzzy set, its entropy is zero, and that two distinct interval-valued fuzzy sets have the same fuzzy entropy.
Numerical examples show the rationality and practicality of the proposed fuzzy entropy.