Diastereomer
A stereoisomer that is not a mirror image of the compound with which it is compared.
Unit
Dimensionless
In depth
Diastereomers arise when a molecule has two or more stereocentres and the configuration differs at some but not all of them. Unlike enantiomers, they have genuinely different physical properties, so they can be separated by crystallisation, distillation or ordinary chromatography.
Examples in the real world
Threose and erythrose; cis and trans isomers are also formally diastereomers.