In human anatomy, bones and muscles are the structural foundations of the body. They form our shape, strength, and body type, and together they help to engineer movement and force of locomotion. In sociology, structure is a concept that refers to organized social arrangements that create patterns for social engagement. Structure, both anatomically and sociologically, refers to relatively obdurate realities that affect what is possible, and what is not. It is the structure that gives rise to the composition of the human body and to the order of social relations, although in both cases there is a range of variation depending on differences among individual people and the amount of agency they can wield in the world.