Final answer:
A fertilized egg between 9-38 weeks is called a fetus.
Step-by-step explanation:
Fetus: The Name of the Fertilized Egg Between 9-38 Weeks
When a human organism reaches about nine weeks after fertilization, it transitions from being an embryo to a fetus. This is the stage where the fetus takes on the recognizable form of a human being, with the disappearance of the 'tail.'
The fetal stage extends from the beginning of week 9 to about 38 weeks after fertilization, which is the average time of birth.