The buttocks (singular: buttock) are two rounded portions of the anatomy, located on the posterior of the pelvic region of apes (including humans), and many other bipeds or quadrupeds, and comprise a layer of fat superimposed on the gluteus maximus and gluteus medius muscles.
Physiologically, the buttocks enable weight to be taken off the feet while sitting. In many cultures, they play a role in sexual attraction.
Many cultures have also used the buttocks as a primary target for corporal punishment, as the buttocks' layer of subcutaneous fat offers protection against injury while still allowing for the infliction of pain. There are several connotations of buttocks in art, fashion, culture and humor, and the English language is replete with many popular synonyms that range from polite colloquialisms (“posterior” or “bottom”) to vulgar slang. In humans the buttocks are located between the lower back and the perineum.
see Buttock pain.