Illustrated Glossary of Organic Chemistry

Stereocenter (chiral center): An atom with three or more attachments, interchanging of two of these attachments leads to another stereoisomer. Most commonly, but not limited to, an sp3 (tetrahedral) carbon atom bearing four different attachments.

sp3 carbon
sp2 carbon

Sulfur and
                nitrogen stereocenters
Stereocenters at sp3 carbon
Stereocenters at sp2 carbon
Sulfur and nitrogen stereocenters