Evidence-based professional reference pages authored by our clinical team for the use of medical professionals. The letters α and β[18] denote absolute stereochemistry at chiral centers—a specific nomenclature distinct from the R/S convention[19] of organic chemistry to denote absolute configuration of functional groups, known kakım Cahn–Ingold–Prelog priority rules. The R/S http://www.drugoffice.gov.hk/gb/unigb/tr.wikipedia.org/wiki/Vitamin