noun
sister language; cognate language
Linguistics term for a language that shares a common ancestor with another, i.e., a cognate language.
日本語と韓国語は姉妹語である可能性が議論されている。
The possibility that Japanese and Korean are sister languages is debated.
Compound of 姉妹 (shimai, 'sisters') and 語 (go, 'language'), a calque of English 'sister language'.