An associated state is the minor partner or dependent territory in a formal, free relationship between a political entity (some of them dependent states, some of them fully sovereign) and a major party—usually a larger state.
The details of such free association are contained in United Nations General Assembly Resolution 1541 (XV) Principle VI, a Compact of Free Association or Associated Statehood Act and are specific to the countries involved. In the case of the Cook Islands and Niue, the details of their free association arrangement are contained in several documents, such as their respective constitutions, the 1983 Exchange of Letters between the governments of New Zealand and the Cook Islands, and the 2001 Joint Centenary Declaration.