According to the Vienna Convention on the Law of Treaties of 23 May 1969, a treaty is an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments. It can be bilateral (between two States) or multilateral (between more than two States). There are multiple uses of the term treaty and it does not necessarily correspond to a precise use. The terms that have been used are : Covenant (of the League of Nations, of the Arab League) ; Protocol (Additional Protocol to the Covenant on Civil and Political Rights) ; Charter (United Nations, Organization of African Unity) ; Constitution (this is the term used for the ILO constituent agreement), not to be confused with the internal Constitutions of States ; Convention (e.g., Elimination of All Forms of Racial Discrimination). States which ratify a treaty or adhere to it, are obliged to respect it.
*See : Adherence, Charter, Convention, Covenant, Entry into Force, Protocol, Reserve.