gemelas

Gemelas is the Spanish term for two female twins. The word comes from the feminine form of gemelo; in Spanish, gemela describes a female twin, and gemelas refers to a pair of female twins. In Portuguese, the corresponding term is gêmeas, with a different spelling. The plural form gemelas is commonly used to describe sisters who were born from the same pregnancy.

Twins arise when a fertilized egg splits (monozygotic, identical twins) or when two eggs are fertilized (dizygotic, fraternal twins). Monozygotic twins share nearly identical genetic material, while dizygotic twins are as genetically similar as ordinary siblings. Placental and amniotic arrangements may vary depending on the type, with monozygotic twins often sharing a placenta in some cases and dizygotic twins always having separate placentas.

Frequency varies by type and population. Monozygotic twinning occurs at a relatively constant rate worldwide, about 3–4 per 1,000 births. Dizygotic twinning rates differ by ethnicity, maternal age, parity, family history, and the use of assisted reproductive technologies, being higher in some African populations and lower in parts of Asia and Europe.

Cultural significance also varies. In many societies, twins are seen as symbols of luck, duality, or special kinship, and they may be the focus of rituals, naming practices, or social expectations. In others, myths or superstitions surrounding twins have shaped local beliefs.

Twins have been important in scientific research through twin studies that compare monozygotic and dizygotic twins to understand genetic and environmental influences on traits and diseases. The topic remains relevant across genetics, developmental biology, and medicine.