This volume is a translation and revision of the Original Russian version by Baryahktar. It covers all of the main fields involved in Condensed Matter Physics, such as crystallography, electrical properties, fluids, magnetism, material properties, optics, radiation, semiconductors, and superconductivity, as well as highlights of important related subjects such as quantum mechanics, spectroscopy, and statistical mechanics. Both theoretical and experimental aspects of condensed matter are covered in detail. The entries range from very short paragraphs on topics where definitions are needed, such as Bloch's law, clathrate compound, donor, domain, Kondo lattice, mean free path, and Wigner crystal, to long discussions of more general or more comprehensive topics such as antiferromagnetism, crystal lattice dynamics, dislocations, Fermi surface, Josephson effect, luminescence, magnetic films, phase transitions and semiconductors. The main theoretical approaches to Condensed Matter Physics are explained. There are several long tables on, for example, Bravais lattices, characteristics of magnetic materials, units of physical quantities, symmetry groups. The properties of the main elements of the periodic table are given.