Public companies are formed within the legal systems of particular states, and therefore have associations and formal designations which are distinct and separate in the polity in which they reside. In the United States, for example, a public company is usually a type of corporation (though a corporation need not be a public company), in the United Kingdom it is usually a public limited company (plc), in France a "société anonyme" (SA), and in Germany an Aktiengesellschaft (AG). While the general idea of a public company may be similar, differences are meaningful, and are at the core of international law disputes with regard to industry and trade.