1) Ratification : a treaty is generally open for signature for a certain time following the conference which has adopted it. However, a signature is not binding on a State unless it has been endorsed by ratification. The time limits having elapsed, the Conventions and the Protocols are no longer open for signature. The States which have not signed them may at any time accede or, in the appropriate circumstances, succeed to them.
Accession : instead of signing and then ratifying a treaty, a State may become party to it by the single act called accession.
2) Reservation / Declaration : unilateral statement, however phrased or named, made by a State when ratifying, acceding or succeeding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State (provided that such reservations are not incompatible with the object and purpose of the treaty).
3) Declaration Article 90 : Declaration provided for under Article 90 of 1977 Additional Protocol I (prior acceptance of the competence of the International Fact-Finding Commission).