Wikipedia defines diffraction as -
Diffraction is the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture.
So, we can say that the bending of any light waves around any object is diffraction.
Now, I was reading the book Introduction to Solid State Physics by Charles Kittel and I came across the following line on page 37, Chapter 2 of the fifth edition of the book.
The diffraction depends on the crystal structure and on the wavelength. At optical wavelengths such as 5000Å the superposition of the waves scattered elastically by the individual atoms of a crystal results in ordinary optical refraction.
So in this way it appears that the book is hinting that refraction is simply a special case of diffraction in which the wavelength of light is much larger than the interatomic spacing.
Is this true or have I completely misunderstood the line in the book?