Illustrated Glossary of Organic Chemistry

Bond order: The number of covalent bonds shared between two atoms. When the atoms share one pair of electrons, they have a single bond (bond order = 1). A double bond (bond order = 2) consists of two electrons pairs, while sharing three electron pairs results in a triple bond (bond order = 3). Bond order can be fractional; for example, a partial pi bond resulting from resonance has a bond order between 1 and 2.