Cervical lordosis is a curve in the cervical spine, the area of the spine which contains the neck vertebrae. This curve is entirely normal and in fact desirable because it helps to stabilize the head and spine, but when the curve straightens out, becomes too deep, or faces in the wrong direction, it can become a problem.
If something's canonical, it follows a principle or rule, usually in a religious or church-related situation. It is also used in mathematics, music and can refer to something reduced to its most basic form.
Canonical coordinates, sets of coordinates which can be used to describe a physical system at any given point in time. Canonical form, a natural unique representation of an object, or a preferred notation for some object.