ABSTRACT
In this chapter, the authors investigate the interpolation property. Roughly speaking there are two methods of interpolation. One depends on the structure of the function spaces composed of real-valued functions, and is called the real interpolation. The authors consider the real interpolation of quasi-Banach spaces. They provide interpolation formulas and examples and show a concrete example by interpolating Lebesgue spaces. The interpolation of Morrey spaces dates back to the 1960’s. Campanato and Murthy, Spanne and Peetre obtained some results on the boundedness of operators in Morrey spaces and interpolation spaces. The notion of generalized local Morrey spaces will play a key role. Consequently, the interpolation of Morrey spaces is more difficult than that of Lebesgue spaces.
