phen-comb. form
Stress is usually determined by a subsequent element and vowels may be reduced accordingly; see e.g.
phenformin n.Origin: A variant or alteration of another lexical item. Etymon: pheno- comb. form.
Etymology: Variant of pheno- comb. form, probably arising from forms with phen- before a second element beginning with a vowel, hence being extended to second elements beginning with a consonant.Found in a number of drug names from the mid 20th cent., e.g. phentolamine n., phenmetrazine n., phenformin n., phencyclidine n.
This entry has been updated (OED Third Edition, December 2005; most recently modified version published online January 2018).