Describing chemical compounds containing an azo group (N=N), a double bond between two nitrogen atoms, commonly found in dyes and pigments.
From German 'Azofarbstoffe' (azo dyes), itself from 'azo-' possibly meaning 'without oxygen' or from 'azoic' (pertaining to life). Entered English in the 1870s as synthetic dye chemistry exploded.
Azo dyes revolutionized fashion and industry—instead of using rare natural dyes, chemists could synthesize millions of colors from coal tar, which is why your clothes are probably colored with azo compounds.
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