The Elvish language created by J.R.R. Tolkien that means “the language of the Quendi” is Quenya.
Quenya is one of Tolkien’s most developed constructed languages. In his linguistic mythology, it was associated especially with the Eldar and was influenced by Finnish, Latin, and other languages Tolkien studied or admired. Its vocabulary and grammar changed across Tolkien’s lifetime as he revised the history behind it.
Within the fiction, Quenya was an ancient and prestigious Elvish language. It remained important in formal names, poetry, and ceremonial usage, even after Sindarin became more widely spoken among many Elves in Middle-earth. The word Quendi refers broadly to the Elves, the “Speakers” who awoke in the distant past.
Quenya is often confused with Sindarin because both are major Elvish languages in Tolkien’s legendarium. Sindarin was the everyday language of many Elves in Beleriand and later Middle-earth, while Quenya carried older, more formal associations.