What does dizygotic mean?
Dizygotic is an adjective used mainly in genetics, medicine, and developmental psychology to describe embryos or twins that arise from two separate fertilized eggs. When a woman releases two eggs in a single cycle and both are fertilized by sperm, the resulting pair of embryos is dizygotic; such twins are also called fraternal or non-identical, because each develops its own placenta and its own unique genetic makeup, making them genetically comparable to ordinary siblings who merely shared a gestation period. The word contrasts directly with monozygotic, which describes identical twins derived from one egg that splits after fertilization. Dizygotic is formal and scientific in register — it rarely appears outside clinical papers, textbooks, and informed discussion of heredity, where researchers rely heavily on comparisons between dizygotic and monozygotic twins to separate genetic influences from environmental ones. Its Greek roots, meaning literally 'two-yoked,' make it both precise and etymologically transparent to anyone familiar with terms like zygote.
adjectiveDeveloped from two separately fertilized eggs; relating to or denoting twins formed from two distinct zygotes that are genetically as different from each other as ordinary siblings.
- (of twins or embryos) developed from two separately fertilized eggs rather than a single fertilized egg
"The study compared the academic performance of dizygotic and monozygotic twins raised apart."
"Roughly two-thirds of all twin pregnancies are dizygotic."
"Because they were dizygotic, the brothers looked no more alike than any other pair of siblings."
Dizygotic twins share a womb but not DNA — they're essentially ordinary siblings who happened to be born on the same day.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dizygotic
Dizygotic derives from the Greek prefix 'di-' meaning 'two' combined with 'zygote,' which itself comes from the Greek 'zygon,' meaning 'yoke' or 'pair.' The underlying metaphor is that of two cells yoked together at fertilization. It emerged as a technical term in early twentieth-century biology, alongside related coinages such as monozygotic, as scientists began distinguishing between twin types based on their embryonic origin. Cognates sharing the zygon root include zygote, homozygous, heterozygous, and even parasite (originally 'one who eats beside another at a shared table').
Related word forms
How dizygotic is actually used
A technical term used chiefly in genetics, embryology, and medical writing; in everyday speech 'fraternal' or 'non-identical' is more common. The stress pattern is variable, with primary stress sometimes heard on the second syllable.
Easily confused with dizygotic
Monozygotic twins develop from a single fertilized egg and are genetically identical, whereas dizygotic twins develop from two separate eggs and are no more alike genetically than ordinary siblings.