Author J. R. R. Tolkien created many languages for his Elves, which eventuated in the creation of a mythology, complete with races, to speak the languages he had constructed. The language has quickly spread among modern day use, resulting in Quenya and Sindarin to become legally stated languages. His interest was primarily philological, and he said his stories grew out of his languages. The languages were the first thing Tolkien created for his mythos, starting with what he originally called "Qenya", the first primitive form of Elvish. This was later called Quenya and is one of the two most complete of Tolkien's languages. The phonology and grammar of Quenya are strongly influenced by Finnish, Latin, Greek and elements of ancient Germanic languages, and Sindarin is strongly influenced by Welsh. Tolkien conceived a family tree of Elvish languages, all descending from a common ancestor called Primitive Quendian. He worked extensively on how the languages diverged from Primitive Quendian over time, in phonology and grammar, in imitation of the development of real language families. In addition to Quenya and Sindarin, he sketched several other Elvish languages in far less detail, such as Telerin, Nandorin, and Avarin. In addition to Tolkien's original lexicon, many fans have contributed words and phrases, attempting to create a language that can be fully used in reality.
Other Elvish languages
Since Tolkien, others have invented Elvish languages in their own fiction. Several borrow sounds and forms from Tolkien's Elvish languages, especially Quenya, while others are quite distinct, for example the Elvish spoken in the book titled Elvish, by S.G. Prince.
Elven, the language of RuneScape's Elves, is basically Welsh with a slight twist.
The Ancient Language The language of the elves in The Inheritance Cycle. Also used by the riders and other magic users to cast spells. It was based on Old Norse and was the language of the now extinct Grey Folk. One cannot lie in the Ancient Language and is bound by what one says in it.
Elven, the language of the surface Elves of Dungeons & Dragons.
Ellylon and Hen Llinge - elvish languages of Andrzej Sapkowski's The Witcher saga, based on Welsh, Irish, French and English.
The Elvish language of the Warcraft universe, are not described in detail but superficially resemble Tolkien's. Together, Darnassian, Nazja, and Thalassian are considered the modern elvish tongues of the Warcraft universe spoken by the modern Kaldorei, the Naga, and the highborne while Elvish itself is considered an ancient tongue that is no longer used as a primary language. It is assumed that Elvish is the language from which Darnassian evolved; Darnassian then branched into Nazja, spoken underwater by the kaldorei that followed Queen Azshara after the sundering, and later on, Thalassian, which is spoken by the highborne as well as the Blood Elves.