The term "fertilized cell" can also be referred to as a zygote, which is the result of the fusion of two haploid cells (egg and sperm) during fertilization. Another synonym for fertilized cell is an embryo, which is the early developmental stage of an organism after fertilization. It is also commonly referred to as a blastomere, where the zygote undergoes rapid cell division, resulting in a cluster of cells known as a blastocyst. Moreover, a fertilized cell can also be called a conceptus, which refers to the product of conception. Other commonly used terms for the fertilized cell include a fertilized egg, germ cell, and ovum.