Although the terminology is inseparable from content the article discusses mainly terminological side of the phenomenon. Using comparative, linguistic methods, content analysis, the author examines terminology used in British, French, German, some other constitutions, including the сonstitutions in Slavic languages, other legal acts, international documents to refer to the concepts of «state of law» and «rule of law» (sometimes also used the term «supremacy of law»), showing the differences in the origin, content and meaning of these phrases in Russian, some other Slavic languages, and other languages in Western Europe. The article listed the shortcomings of some terms, limit the content of the rule of law concept by higher legal force of the Constitution, the constitutionality, legality or the special role of the law in the system of sources of law. The author examines the definitions of «rule of law», which given some credible international organizations offers clarification of these definitions.