The human pelvic girdle is a masterpiece of divine creation! It is the synchronous melding of bone to bone, joining the legs to the spinal column in a supple, strong fashion as well as creating a basin to house the digestive, eliminatory, and reproductive organs of the body.
Pelvis means "basin" in Latin. It is made up of some queer bones called "ossa innominata" or "bones without a name". The reason why is because they are so irregular in shape, it's hard to know if they are all one bone or a series of bones joined together! To simply things, scientists have broken down the innominate bones into three basic parts: ilium, ischium, and pubis.
The ilium is the uppermost prominent bone of the pelvis and is often referred to as the "groin" or "flank". It is also the widest part of someone's hips and the part you can feel the most. The ischium forms the lower and back part of the hip and is referred to as the "hip". It's also the part of the pelvis that the leg is attached to via a ball and socket joint and many ligaments and connective tissue. The pubis is the "floor" of the pelvis and the bones we feel when we're sitting. The male and female pelvis are shaped differently, the female pelvis having the capability for spreading wider during childbirth. The birthing child descends through a special opening in the female pelvis called "the birth canal." The hips attach to the spinal column via the sacrum, the lower continuation of the spinal column and above the coccyx, or "tip of the spine."
So, remembering the song, "Them Bones, Them Bones," it goes like this: "The thigh bone's connected to the hip bone; the hip bone's connected to the backbone; the backbone's connnected to the headbone . . . " and so on and so forth! It's really quite ingenious and also very strong! The upper body rests on the hips, the hips rest on the legs, and everything's held together by ligaments and connective tissue.
By the way, I looked up each one of the names of the bones in a dictionary, the World Book Encyclopedia, and on Wikipedia.com.