Glossary Terms and Definition

Co-twin or co-multiple:  One child of a multiple birth set 

Conjoined twins: Twins born attached and sharing body; once referred to as “Siamese” twins  

Fraternal:  Dizygotic or two egg twins resulting from the separate fertilization of two ova;fraternal siblings have their own unique genes and may be same sex or different sex. 

Higher order multiples: A multiple birth set consisting of three or more children (triplets, quadruplets,quintuplets, etc) 

Identical: Monozygotic, or one egg twins, result from one fertilized egg spitting.Monozygotic twins have all their genes in common; they have identicalfeatures, eye and hair color.                                                           

Mirror image twins: Occurs only in monozygotic twins; about 23 percent of identical twins will have features displayed on opposite sides of the body or “mirror images”of their twin; this may explain why a little over one-third of identical twins are left-handed. 

Multiple birth children: A group of two (twins) or more (higher order) children who typically are conceived at the same time of the same parents, are born at the same time,and share a certain biological and genetic make-up. 

Singleton: A child who is not part of a multiple birth set. 

Supertwins: Multiple births of three or more including triplets, quadruplets, andhigher-order multiples 

Twintyping: Determination of twin type through testing; experts suggest DNA testing   

Figure 1 from dissertation page 27 - Glossary terms and definitions (NOMOTC [2002], 4, 51-52; Jackson 2001, 20-21, 24). (