That is incorrect. Subduction is when one plate moves under another.
It is the lithosphere that is broken into tectonic plates, which undergo some large-scale motions. The boundary regions between plates are aptly called “plate boundaries.” Based upon their motions concerning one another, these plate boundaries are of three kinds: divergent, convergent, and transform.
Saturn is predominately composed of hydrogen and helium, yet doesn't undergo fusion like the Sun due to the lacking mass.
