levorotatory

adj. turning toward the left (Optics, Chemistry)

Levororatory (also Laevorotation, Latin: laevus, left) refers to the substance that rotates polarized light in a counterclockwise direction. This rotation, measure in degrees, is said to be negative (-). A clockwise, positive (+), direction of rotation is called dextrorotatory (Latin: dexter, right).
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Adjective
1. rotating to the left
(synonym) levorotary, left-handed
(similar) counterclockwise, anticlockwise, contraclockwise

(a.)
Turning or rotating the plane of polarization towards the left; levogyrate, as levulose, left-handed quartz crystals, etc.
  

Compare with dextrorotatory .Having the property of rotating plane-polarized light counterclockwise.