What is the term for a fertilized ovum or embryo?

The term for a fertilized ovum or embryo is "zygote." This terminology is used to describe the initial single cell that forms when a sperm cell fertilizes an egg cell. The zygote represents the very beginning of human development and is a crucial stage in the reproductive process. Following fertilization, the zygote undergoes several series of divisions and transformations before developing into an embryo, which is a later stage in the developmental process.

The other terms provided refer to different concepts related to human development. "Embryo" refers to the stage of development after the zygote has begun dividing and growing, and it encompasses a broader period of development before the fetus stage. "Gene" denotes a segment of DNA that contains information for the synthesis of proteins and is crucial for hereditary traits, but it does not refer to the structure formed after fertilization. "Embryonic stage" describes the specific phase of development of the embryo, typically lasting from weeks 3 to 8 of pregnancy, after the initial zygote stage has passed. Thus, "zygote" is the precise term for the fertilized ovum.