A fetus or foetus (/ˈfiːtəs/; plural fetuses, feti, foetuses, or foeti) is the unborn offspring of an animal that develops from an embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal development begins from the ninth week after fertilisation (or eleventh week gestational age) and continues until birth. Prenatal development is a continuum, with no clear defining feature distinguishing an embryo from a fetus. However, a fetus is characterized by the presence of all the major body organs, though they will not yet be fully developed and functional and some not yet situated in their final anatomical location.

 

Note:   The above text is excerpted from the Wikipedia article Fetus, which has been released under the GNU Free Documentation License.