-( ə )nəl adjective
Etymology: Latin vicinalis, from vicinus neighbor (from vicinus neighboring) + -alis -al
1. : of, relating to, or confined to a limited district or neighborhood : belonging to or restricted to a vicinity : local
vicinal roads are distinguished from through highways
2. : of, relating to, or being the subordinate forms or faces on a crystal which sometimes take the place of the fundamental ones, approach them very closely in angle, and have in general very complex symbols
3. : relating to, characterized by, or being adjoining positions in an organic chemical compound
the three vicinal 1,2,3-positions in benzene
— abbr. v ; compare neighboring 2, ortho I 2