Hello BingBing: The answer depends upon the specific context. Waist is simple enough to understand, because it refers to human anatomy just above the Pelvic Bone and going around the soft tissue of the abdomen. Loin can have various interpretations, varying from Hips to inner leg to genitalia. Meanings have to be inferred from their usage.--Warm Regards, Bruce

In real world scenarios you will probably only hear loin used in the Bible, and referring to cuts of meat. Or perhaps in biology/veterinary class studying an anatomy chart.