The term treaty can be used as a common generic term or as a particular term which indicates an instrument with certain characteristics.
- Treaty as a generic term: The term 'treaty' has regularly been used as a generic term embracing all instruments binding at international law concluded between international entities, regardless of their formal designation. Both the 1969 Vienna Convention [PDF, 458 KB] and the 1986 Vienna Convention [PDF, 596 KB] confirm this generic use of the term 'treaty'. The 1969 Vienna Convention defines a treaty as "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 and whatever its particular designation". The 1986 Vienna Convention extends the definition of treaties to include international agreements involving international organizations as parties. In order to speak of a 'treaty' in the generic sense, an instrument has to meet various criteria. First of all, it has to be a binding instrument, which means that the contracting parties intended to create legal rights and duties. Secondly, the instrument must be concluded by states or international organizations with treaty-making power. Thirdly, it has to be governed by international law. Finally the engagement has to be in writing. Even before the 1969 Vienna Convention on the Law of Treaties, the word 'treaty' in its generic sense had been generally reserved for engagements concluded in written form.
- Treaty as a specific term: There are no consistent rules when state practice employs the terms 'treaty' as a title for an international instrument. Usually the term 'treaty' is reserved for matters of some gravity that require more solemn agreements. Their signatures are usually sealed and they normally require ratification. Typical examples of international instruments designated as 'treaties' are Peace Treaties, Border Treaties, Delimitation Treaties, Extradition Treaties and Treaties of Friendship, Commerce and Cooperation. The use of the term 'treaty' for international instruments has considerably declined in the last decades in favor of other terms.