Levo- \Le"vo-\ (l[=e]"v[-o]-). A prefix from L. laevus, meaning:
   (a) Pertaining to, or toward, the left; as, levorotatory.
   (b) (Chem. & Opt.) Turning the plane of polarized light to the left; as, levotartaric acid; levoracemic acid; levogyratory crystals, etc. [Written also l[ae]vo-.]

Source: Webster's Revised Unabridged Dictionary (1913)