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.
For many, the word literature suggests a higher art form, merely putting words on a page doesn't necessarily mean creating literature. A canon is the accepted body of works for a given author. Some works of literature are considered canonical, that is culturally representative of a particular genre.