In human development, a fetus or foetus (/ˈfiːtəs/; plural fetuses or foetuses) is the prenatal stage between the embryonic state and birth. The fetal stage of human development tends to be taken as beginning at the gestational age of eleven weeks, (nine weeks at fertilization age).[1][2] However, prenatal development is a continuum, with no clear defining feature distinguishing an embryo from a fetus. A fetus is also 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.