The writing system created by Fëanor in J.R.R. Tolkien’s legendarium is Tengwar.
Tengwar, also called the Fëanorian characters, is a script invented within Tolkien’s mythology by Fëanor, an Elf of the Noldor. It is used to write several languages, including Quenya and Sindarin, and appears in many forms across the histories of Middle-earth.
The script’s design was part of Tolkien’s broader interest in the relationship between language, sound, and writing. Unlike an alphabet tied to only one language, Tengwar can represent different languages through differing conventions and modes. This is why the same script may look similar while spelling systems vary.
Tengwar is often confused with Cirth, another Middle-earth writing system. Cirth consists of angular runes associated especially with the Sindar and later with dwarves, while Tengwar is the more flowing script traditionally associated with Fëanor. Tolkien also developed Sarati, an earlier writing system linked to Rúmil.