- The pelvic girdle or bony pelvis, the irregular ring-shaped bony structure connecting the spine to the femurs (thigh bones),
- The pelvic cavity, the space enclosed by the pelvic girdle,
- The pelvic region.
In the adult human, the pelvis is formed in the posterior dorsal (back) by the sacrum and the coccyx (the caudal part of the axial skeleton), and laterally and anteriorly by a pair of hip bones (part of the appendicular skeleton or lower extremity). In an adult, the pelvis is thus composed of three large bones plus the coccyx (3-5 bones). However, before puberty each hip bone consists of three separate bones yet to be fused — the ilium, ischium, and pubis. Thus, before puberty the pelvis can consist of more than ten bones, depending on the composition of the coccyx.