Illustrated Glossary of Organic Chemistry

Levorotatory (l; (-)): A substance that rotates plane polarized light in a counterclockwise direction. Indicated by including (-) before the compound name, or in the older literature, l, such as (-)-nicotine or (l)-nicotine.

Pass through (S)-(-)-nicotine solution

Plane of polarization before
(S)-(-)-nicotine solution.

Plane of polarization after
(S)-(-)-nicotine solution.
Passing plane-polarized light through a solution of (S)-(-)-nicotine causes the plane of polarization to be rotated to the left (a counterclockwise direction; as indicated by the red arrow), demonstrating that this molecule is optically active and levorotatory.