Tengwar is the fictional script Tolkien used for the Ring inscription. The Tengwar, also called the Fëanorian characters, is a writing system created by Tolkien for the languages of Middle-earth.
The One Ring’s inscription is written in Tengwar characters, although the words themselves are in the Black Speech of Mordor. This distinction matters: a script is a writing system, while a language is the spoken or written form being represented. The inscription begins with the famous words “Ash nazg durbatulûk.”
Tolkien created several writing systems for his fictional world. Cirth is a runic script used especially by Dwarves and also by other peoples, while Sarati is an earlier system associated with the Elves. These scripts should not be treated as interchangeable.
The Ring inscription is found on the Ring when heated by fire and is described in The Fellowship of the Ring. Its circular arrangement and distinctive letter forms helped make Tolkien’s invented writing systems recognizable beyond the books.