As used in 42-10-121 through 42-10-128, the following definitions apply: (1) "Adoption assistance agreement" means an agreement for adoption assistance between adoptive parents and the state child welfare agency of the state that undertakes to provide the adoption assistance, including a subsidy agreement as provided in 42-10-108. (2) "Adoption assistance state" means the signatory state to an adoption assistance agreement in a particular case. (3) "Residence state" means the state of which the child is a resident by virtue of the residence of the adoptive parents. (4) "State" means a state of the United States, the District of Columbia, the Commonwealth of Puerto Rico, the Virgin Islands, Guam, the Commonwealth of the Northern Mariana Islands, or a territory or possession of or administered by the United States.