A twin is one of two offspring produced in the same pregnancy. Twins can either be monozygotic ("identical"), meaning that they develop from one zygote that splits and forms two embryos, or dizygotic ("fraternal") this is because they develop from two separate eggs that are fertilized by two separate sperm.
In contrast, a fetus which develops alone in the womb is called a singleton, and the general term for one offspring of a multiple birth is multiple.
Famous quotes containing the word twin:
“We live under continual threat of two equally fearful, but seemingly opposed, destinies: unremitting banality and inconceivable terror. It is fantasy, served out in large rations by the popular arts, which allows most people to cope with these twin specters.”
—Susan Sontag (b. 1933)
“That Dali is really Norman Rockwells twin brother kidnapped by gypsies in babyhood.”
—Vladimir Nabokov (18991977)
“If they be two, they are two so
As stiff twin compasses are two;
Thy soul, the fixed foot, makes no show
To move, but doth if th other do.”
—John Donne (15721631)