@JeremyECrawford Do Drow PCs know Undercommon? What about the Drow Sign Language? RAW it doesn't look like it.

— Makankosappo✨🧙 (@PyrrhicPlays) November 5, 2018

The races presented in the "Player's Handbook" know the languages in their language entries.

A monstrous member of a race has no bearing on how a playable member of that race works. #DnD https://t.co/CYjCSHw7SL

— Jeremy Crawford (@JeremyECrawford) November 5, 2018