This fatty acid has been referred to as (9Z)-Octadec-9-enoic acid,(9Z)-Octadecenoic acid, (Z)-Octadec-9-enoic acid, cis-9-Octadecenoic acid, cis-delta 9-Octadecenoic acid and C18:1 cis-9. CAS number 112-80-1. Elaidic acid is the trans isomer of oleic acid.