In view of increasing interests in thermal expansion of solid materials, various principles or concepts concerning the thermal expansion phenomenon are illustrated.
The contents of this review article are
1. Introduction and definition of the thermal expansion coefficient.
2. Why thermal expansion occurs.
3. Thermodynamical treatment of thermal expansion.
4. Thermoelastic effect in solids.
5. Effects of phase transformation and magnetic transformation on thermal expansion.
6. Materials having peculiar thermal expansion properties.
7. Conclusion.
