one of a pair of twins who develop from a single fertilized ovum and therefore have the same genotype, are of the same sex, and usually resemble each other closely.
Compare fraternal twin.
Origin of identical twin
First recorded in 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Medicine definitions for identical twins
Twins derived from the same fertilized ovum that at an early stage of development becomes separated into independently growing cell aggregations, giving rise to two individuals of the same sex, identical genetic makeup, and closely similar appearance.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.