the interior system comprises the interior plateau and interior mountains (aka the northern interior mountains) and the southern part of the yukon plateau. the major subdivisions of the interior mountains are the cassiar mountains, omineca mountains, stikine plateau, skeena mountains and hazelton mountains. each has a variety of subranges and some definitions include the tahltan highland and tagish highland which may also be assigned to the boundary ranges of the coast mountains (see next). the major subdivisions of the interior plateau are the nechako plateau, the mcgregor plateau, the fraser plateau (which includes the chilcotin plateau and cariboo plateau and a number of small mountain ranges) and the thompson plateau. the quesnel, shuswap and okanagan highlands which flank the plateau to the east are sometimes seen as part of it, but are officially part of the columbia mountains range-system and are seen as subranges of the adjoining ranges, namely the cariboo mountains and monashee mountains.