J.R.R. Tolkien called the writing system used for Quenya and Sindarin the Tengwar.
Tengwar is a writing system created by Tolkien for the languages of his legendarium. The name is Quenya and means “letters” or “signs.” Its characters are arranged according to a systematic design, with shapes and positions representing different sounds.
The Tengwar was associated particularly with the Elves and was used to write several languages, including Quenya and Sindarin. It is not itself an Elvish language; it is a script. That distinction matters because readers sometimes identify every visible Elvish inscription as a language rather than separating the writing system from the words being written.
Tolkien also created other scripts. Sarati is an earlier system associated with Rúmil, while Cirth consists of runic characters used in different contexts. The broad popularity of Tengwar comes partly from its appearance in calligraphic inscriptions and adaptations of Tolkien’s work.