noun
subdialect
Linguistics term for a dialect subdivision within a larger dialect area.
この地域の下位方言には独特の語彙が残っている。
The subdialects of this region retain unique vocabulary.
方言 is a general term for dialect, while 下位方言 specifically refers to a subdialect, a subdivision within a dialect.
Compound of 下位 (lower rank) and 方言 (dialect), a calque or translation of the English term 'subdialect'.