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.
SEO Best Practice. For SEOs, canonicalization refers to individual web pages that can be loaded from multiple URLs. This is a problem because when multiple pages have the same content but different URLs, links that are intended to go to the same page get split up among multiple URLs.