chiral
the property of "handedness
achiral
molecules that possess a plane of symmetry
meso
molecules that possess both stereogenic centers and a plane of symmetry
isomers
non-superimposable molecules of the same formula. they may have the same or different connectivities
enantiomers
always exist in pairs
optically active
the property of rotating plane polarized light
constitutional isomers
molecules of the same formula with different connectivities
stereoisomers
molecules of the same formula with different connectivities
racemic mixture
50% R, 50% S
diasteromers
stereoisomers that are not mirror images