Definition of "azo" []

• Containing a nitrogen group, especially N=N. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Those include Sunset Yellow and red Ponceau 4R, the so-called azo dyes that give Irn-Bru its hyper-orange sheen."
• "A large number of the dyes prepared from coal tar are called azo colours, such for instance are the Biebrich and Croceine scarlets and oranges, Naphthol black, Congo red, etc., just to name a few."
• "(called azo dyes) must be labeled not only with the relevant E number, but also with the words"