What is a person who speaks four languages?

There isn't a specific word for someone who speaks four languages. However, you could call them:

* Quadrilingual: This is the most accurate term, combining the Latin root "quadri" (four) with "lingual" (language).

* Polyglot: This term generally refers to someone who speaks multiple languages, and it doesn't specify the number.

* Multilingual: Similar to "polyglot," this term broadly describes someone who speaks more than one language.

Ultimately, you can simply say "They speak four languages" or "They are fluent in four languages."