OSPF Terminology
These definitions define relationships among routers:
Neighbor: an adjacent router running OSPF with adjacent interfaces assigned to the same area. Neighbors are found via Hello packets. No routing information is exchanged with neighbors until adjacencies are formed.
Adjacency: a logical connection between a router, its corresponding Designated Router (DR) and Backup DR (BDR). Formation of this relation depends heavily on the type of network that connects the OSPF routers.