The
uterus or
womb is a major female hormone-responsive reproductive
sex organ of most
mammals including
humans. One end, the
cervix, opens into the
vagina, while the other is connected to one or both
fallopian tubes, depending on the species. It is within the uterus that the
fetus develops during
gestation, usually developing completely in
placental mammals such as humans and partially in
marsupials such as
kangaroos and
opossums. Two uteri usually form initially in a female fetus, and in placental mammals they may partially or completely fuse into a single uterus depending on the species. In many species with two uteri, only one is functional. Humans and other higher
primates such as
chimpanzees, along with
horses, usually have a single completely fused uterus, although in some individuals the uteri may not have completely fused. In English, the term
uterus is used consistently within the medical and related professions, while the
Germanic-derived term
womb is more common in everyday usage.