sister language

Etymology
Perhaps a.

Noun

 * 1)  A cognate language; a language that is related to another by virtue of descending from a common ancestral language.

Translations

 * Dutch: zustertaal
 * Finnish: sisarkieli
 * French:
 * Georgian: მონათესავე ენა
 * German: Schwestersprache
 * Hungarian:
 * Italian: lingua sorella
 * Polish: pokrewny język