adjacency

(or contiguity) Two polygons are either adjacent or not. Different criteria may be used to determine adjacency dependent on whether polygons must share an edge (Rook's case) or need only share a corner (Queen's case). Adjacency relations among a set of polygons or areas may be summarized in an adjacency matrix where each row-column entry is either 1 (for adjacent polygons) or 0 (for non-adjacent polygons).