Definition of "monozygotic" []

• Derived from a single fertilized ovum or embryonic cell mass. Used especially of identical twins. (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.

• "Of 5,597 monozygotic twin pairs where both were alive and had provided usable responses to CFS screening questions, we identified 140 pairs of twins who met preliminary inclusion criteria: born 1935-1985, classified as a monozygotic twin based on questionnaire responses"
• "Therefore although I might call them "monozygotic" I wouldn't agree that they were "identical.""
• "In "A Genetic Study of Male Sexual Orientation," a study that has now achieved almost as much renown as LeVay's, the Northwestern University psychologist Michael Bailey and Boston University's Richard Pillard compared fifty-six "monozygotic" twins (identical twins, from the same zygote, or fertilized egg), fifty-four "dizygotic" (fraternal) twins, and fifty-seven genetically unrelated adopted brothers."