Complex sentence: As is the case for the decibel and bel, the neper is a unit of the International System of Quantities (ISQ), but not part of the International System of Units (SI), but it is accepted for use alongside the SI.
Split into simpler sentences: As is the case for the decibel and bel, the neper is a unit of the International System of Quantities (ISQ). It is not part of the International System of Units (SI), but is accepted for use alongside the SI.