* Polyglot: This is the most common and widely recognized term for someone who knows and speaks multiple languages fluently.
* Multilingual: This term simply indicates that someone speaks more than one language. It doesn't necessarily imply expertise or fluency in all the languages.
* Linguist: While a linguist is primarily concerned with the study of language, some linguists may also be skilled in multiple languages.
* Hyperpolyglot: This term is used for someone who can speak 6 or more languages fluently.
The best term to use depends on the context and the level of expertise you want to emphasize.