from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A five-membered heterocycle having three carbon atoms, one oxygen atom, one nitrogen atom and two double bonds; the 1,3- isomer is aromatic

from The Century Dictionary and Cyclopedia

  • n. The unknown mother- substance, C3H4ON, of compounds containing a ring composed of three carbon atoms, one nitrogen, and one oxygen atom.


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