noun
identical twins
Medical and everyday term for twins from a single fertilized egg; contrasts with 二卵性双生児 (fraternal twins).
彼らは一卵性双生児なので、顔がそっくりだ。
They are identical twins, so they look exactly alike.
Fraternal twins from two separate eggs; genetically no more similar than ordinary siblings.
Compound of 一卵性 (monozygotic) + 双生児 (twins). The term is a modern medical coinage.