Reservation refers to a unilateral statement, however phrased or named, made by a State (…) when signing, ratifying, formally confirming, accepting, approving or acceding to a treaty, or by a State when making a notification of succession to a treaty, whereby the State (…) purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State (...).

Interpretative declaration means a unilateral statement, however phrased or named, made by a State (…), whereby that State (…) purports to specify or clarify the meaning or scope of a treaty or of certain of its provisions.

For more Information, see International Law Commission (2011) Guide to Practice on Reservations to Treaties.