The artificial language Tolkien created for the Men of Númenor is Adûnaic. In the mythology of Middle-earth, it was the native language of the Númenóreans and developed from the speech of the Men who settled on Númenor.
Adûnaic appears most substantially in material connected with The Notion Club Papers and Tolkien’s later writings about Númenor. It was intended to have a different linguistic character from the Elvish languages, reflecting the history and identity of Men rather than Elves.
Westron is a related point of confusion: it is the Common Speech used across much of the later Third Age, and Tolkien often presents it as the translated language of the narrative. Adûnaic is specifically tied to Númenor’s people and history, while Westron became a broader lingua franca.