A solid is a sample of matter that retains its shape and density when not confined. The adjective solid describes the state, or condition, of matter having this property. The atom s or molecule s of matter in the solid state are generally compressed as tightly as the repulsive forces among them will allow. Some solids, called crystalline solids, tend to fracture along defined surfaces that have a characteristic shape depending on the arrangement of, and the forces among, the atoms or molecules in the sample. Other solids, known as amorphous solids, lack any apparent crystalline structure. Solid-state chemistry, also sometimes referred to as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials, particularly, but not necessarily exclusively of, non-molecular solids. This book is a general textbook, composed for those with little background knowledge of the subject, but who wish to learn more about the various segments of solid state theory and technology.