What term describes the initial cell formed after the fusion of gametes?

The initial cell formed after the fusion of gametes is known as a zygote. During the process of fertilization, a male gamete (sperm) and a female gamete (egg) combine to form this single-cell entity. A zygote contains a complete set of chromosomes, half contributed by each parent, making it the first cell of a new organism. This stage marks the beginning of development, as the zygote will undergo multiple rounds of cell division and differentiation to eventually form a multicellular organism.

While the term "fertilized egg" is often used interchangeably with zygote, "zygote" specifically refers to the cell resulting from fertilization before it has started other developmental processes. The "diploid cell" term denotes that the zygote contains two complete sets of chromosomes, but it does not specify that it is the initial cell formed after gamete fusion. Bacteria, on the other hand, are prokaryotic cells and are not formed from gametes, making them unrelated to this question.