azo-

before vowels az-, word-forming element denoting the presence of nitrogen, used from late 19c. as combining form of azote (1791), the old term for "nitrogen" (from Greek a- "not, without" (see a- (3)) + zoion "a living being," from PIE root *gwei- "to live"), which was coined in French by Lavoisier & de Morveau because living things cannot survive in the pure gas.