Two individuals derived from two FETUSES that were fertilized at or about the same
time, developed in the UTERUS simultaneously, and born to the same mother. Twins are
either monozygotic (TWINS, MONOZYGOTIC) or dizygotic (TWINS, DIZYGOTIC)
Note générale sur le champ d'application :
human only: for animals use LITTER SIZE; PREGNANCY, TWIN is also available