Lordosis (commonly referred to as swayback, saddle back, or hyper-lordosis) is a medical term used to describe an inward curvature of a portion of the vertebral column. Two segments of the vertebral column, namely cervical and lumbar, are normally lordotic, that is, they are set in a curve that has its convexity anteriorly (the front) and concavity posteriorly (behind), in the context of human anatomy. When referring to the anatomy of other mammals, the direction of the curve is termed ventral. Curvature in the opposite direction, that is, apex posteriorly (humans) or dorsally (mammals) is termed kyphosis. Some animals (notably horses) have naturally concave, lordotic backs.