Equations of state for solids under strong compression

The historical and theoretical background for the different mathematical forms commonly used to represent equations of state (EOS) for solids is reviewed and some criteria are discussed which allow to select some specific forms, which are not only convenient mathematical forms but bring out the physical meaning of the data. Some examples are discussed with emphasis on recent experimental and theoretical data including noble gas solids, simple metals and a few metals with special "anomalies" to illustrate the differences involved in the use of different EOS forms and to point out the specific physical reasons for differences in specific EOS forms.