combining form
Etymology: International Scientific Vocabulary, from normal (I)
1. : parent compound from which (a specified compound) may be regarded as derived (as by removal of side chains from a ring system) — especially in names of terpenes
nor bornane
2. : compound of normal structure isomeric with the one to the name of which it is prefixed
nor leucine
3. : homologue lower by one methylene group — especially in names of steroids and alkaloids
nor cholane
nor nicotine