Non-identical twin, also called fraternal twin, refers to siblings that develop from two separate eggs fertilized by two different sperm cells. There are various terms used to describe non-identical twins. Dizygotic twin, biovular twin, and heterologous twin are all synonyms of non-identical twin. Dizygotic twin means that two zygotes, or fertilized eggs, were involved in the creation of the twins. Biovular twin emphasizes the fact that the twins came from two separate ova. Heterologous twin emphasizes the fact that the twins have different genetic material and come from different fertilizations. Overall, different cultures and regions may use different terms to describe non-identical twins, but they all refer to the same phenomenon.