The term metamorphosis is not used while describing human development. Why?

The term metamorphosis is used to describe a process of development of an organism, where the young ones differ drastically in physical appearance from their adult forms. The body parts of an adult are absent in the young ones. Instead, some other and different body parts may be present.

In humans, the body structure of a young one is similar to that of an adult human. All body parts and organs of an adult are present in a child also. Thus, it is not called metamorphosis.