The writing system Tolkien used for many languages of Middle-earth is Tengwar.
Tengwar is a script created by Tolkien for use with several languages in his fictional world. Its name comes from the Quenya word for “letters.” The system is associated especially with the Elves and appears in inscriptions, manuscripts, and the title page of The Lord of the Rings.
Tengwar is an adaptable writing system rather than a single alphabet tied to one spoken language. Different modes assign its signs and vowel marks to different sounds, allowing it to represent languages such as Quenya, Sindarin, and English. This flexibility reflects Tolkien’s interest in historical linguistics and writing systems.
A frequent confusion is between Tengwar and Cirth. Cirth is a separate runic script whose individual signs are called cirth. Angerthas refers to an expanded arrangement of runes, while Sarati is an earlier script in Tolkien’s invented history.