Today's Word of the Day means...
stereoisomer ster·e·o·i·so·mer (stěr'ē-ō-ī'sə-mər, stēr'-)
A molecule containing the same number and kind of atomic groupings as another but having a different spatial arrangement, thus exhibiting different properties.
Any of two or more isomers having the same linkages between the atoms but differing in the way these atoms are arranged in space. There are two types of stereoisomers, geometric isomers and enantiomers. Compare structural isomer.