The fact that we must now distinguish between type-1 and type-2 MFs is one example of the new terminology. A lot of the new terminology is due to the three-dimensional nature of a type-2 MF. Another term that we have already explained is the FOU. Some other new terms are: primary membership, primary MF, secondary grade, secondary MF, secondary set, upper and lower MFs, principal MF, embedded type-1 fuzzy set, and embedded type-2 fuzzy set. All of these terms can be defined mathematically and let us communicate effectively about type-2 fuzzy sets.