Directly:
* Lingua: (Latin) Tongue, language
* Linguistic: Relating to language
* Linguist: A person who studies languages
* Linguistics: The study of language
Indirectly:
* Bilingual: Able to speak two languages
* Multilingual: Able to speak multiple languages
* Unilingual: Able to speak only one language
* Lingual: Relating to the tongue or language
* Sublingual: Situated under the tongue
* Interlingual: Relating to or involving different languages
Less common:
* Lingua franca: A language that is used for communication between people who speak different languages
* Lingua terminalis: A language that is no longer spoken
* Lingua mortua: A dead language
These are just a few examples, and there are many other words that contain the root "lingua". You can often find words containing this root in fields related to language, such as linguistics, translation, and communication.