Here's a breakdown of the terms used for a developing baby:
* Zygote: This is the single cell formed when a sperm fertilizes an egg.
* Embryo: This stage lasts from about two weeks after fertilization to the eighth week of pregnancy. During this time, major organs and body systems develop.
* Fetus: From the ninth week of pregnancy until birth, the developing baby is called a fetus. This is the stage where the baby continues to grow and mature.
So, the term "zygote" is the most accurate term for a developing baby in the earliest stages.