Public International Law (Vol. I & II)
Article 2
For the purposes of the present Convention:
(a) "treaty" means 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;
(b) "ratification", "acceptance", "approval" and "accession" mean the international act whereby a State establishes on the international plane its consent to be bound by a treaty;
(c) "full powers" means a document emanating from the competent authority of a State designating a person or persons to represent the State in relation to a treaty;
(d) "reservation" means a unilateral statement whereby a State purports to exclude or modify the legal effect of certain provisions of a treaty in their application to that State.