The terms 'federalism' and 'confederalism' both have a root in the Latin word foedus, meaning treaty, pact or covenant. Their common meaning until the late eighteenth century was a simple league or inter-governmental relationship among sovereign states based upon a treaty. They were therefore initially synonyms. It was in this sense that James Madison in Federalist 39 had referred to the new United States as 'neither a national nor a federal Constitution, but a composition of both' (ie. neither a single large unitary state nor a league/confederation among several small states, but a hybrid of the two). In the course of the nineteenth century the meaning of federalism would come to shift, strengthening to refer uniquely to the novel compound political form, while the meaning of confederalism would remain at a league of states. Thus, this article relates to the modern usage of the word 'federalism'.