What term describes twins that originate from a single egg cell after fertilization?

Identical twins are formed from a single fertilized egg that splits into two separate embryos. This process results in two genetically identical individuals because they share the same genetic material from the original zygote. This unique formation leads to identical twins having the same DNA, which is the reason they are often referred to as "monozygotic twins."

In contrast, fraternal twins develop from two separate eggs fertilized by two different sperm cells, resulting in siblings who are genetically distinct from one another. Half-siblings arise from different combinations of parents and share only some of their DNA. Hence, the terminology for identical twins is specifically tied to their origin from a single egg, clarifying the genetic relationship they share.