A gomphosis is actually not classified as an amphiarthrosis; instead, it is considered a type of fibrous joint. In anatomical terms, a gomphosis refers specifically to the peg-in-socket joint that occurs, for example, between the teeth and the alveolar sockets in the jaw. Each tooth is held in place by a dense connective tissue known as the periodontal ligament.
On the other hand, an amphiarthrosis is a category of joints that allows for a limited amount of motion; they are more flexible than diarthroses (freely movable joints) but less so than synarthroses (immovable joints). Examples of amphiarthroses include the joints between the vertebrae or the pubic symphysis.
In summary, while both gomphosis and amphiarthrosis are types of joints, they differ in structure and function. Gomphosis is a specialized, fibrous joint with minimal movement, whereas amphiarthroses provide a greater range of motion between the connected bones.