β-

a prefix designating (1) the second carbon atom of a chain starting with that adjacent to the principal functional group, e.g., β-hydroxybutyric acid (see α-); (2) the specific rotation of an optically active substance, e.g., β-D-glucose; (3) the orientation of an exocyclic atom or group, e.g., cholest-5-en-3-β-ol (cholesterol); (4) a plasma protein migrating with the β band (subdivided into β₁ and β₂ bands) in protein electrophoresis, e.g., β-lipoprotein; (5) one in a series of related chemical compounds, particularly a series of stereoisomeric, isomeric, polymeric, or allotropic forms, e.g., β-carotene; and (6) one in a group of related entities, e.g., β-ray. For compounds prefixed with the symbol β-, see the unprefixed form.