Definition

Noun: A monozygous twin is one of a pair of twins who develop from a single fertilized egg (zygote) that splits into two separate embryos. As a result, monozygous twins share identical genetic material and are always of the same sex.

Usage

The term is used in biological, medical, and general contexts to describe a specific type of twinning, emphasizing the shared genetic origin. - The study compared the health outcomes of monozygous twins raised in different environments. - Because they are monozygous twins, they have nearly identical DNA.

Advanced Usage

• Scientific/Medical Context: The term is precise and preferred in genetics and embryology. It is often contrasted with "dizygous twin" (fraternal twins).
  • Researchers recruited pairs of monozygous twins to study the heritability of the trait.

Variants and Related Words

• Monozygotic twin: A fully synonymous term. "Monozygotic" is the adjectival form derived from "monozygotic."
  • Monozygotic twinning is a random event.
• Identical twin: The common, everyday term for a monozygous twin. It highlights the physical resemblance.
• Dizygous twin / Fraternal twin: The antonym; twins developed from two separate fertilized eggs.

Synonyms

• Identical twin
• Monozygotic twin

Notes on Meaning

The core meaning is defined by the single-zygote origin. While "identical twin" is a perfect synonym in most contexts, "monozygous/monozygotic twin" is the technically accurate term in science. It does not imply that the twins are perfectly identical in every way (e.g., fingerprints, personalities), only that they share the same genome at conception.

Noun

1. either of two twins developed from the same fertilized ovum (having the same genetic material)