What is the definition or description of: kyphosis?

See below: When viewing the human spine from the side, there are usually three natural curvatures. The neck and low back have a curvature with the con cavity backward, this is known as lordosis; and the mid back has a curve with the concavity anteriorly, this is known as s kyphosis. When an elderly lady has an increase "hump" in this curvature in the mid back we call it a hyper kyphosis.