The Lhammas is a work of fictional sociolinguistics by J. R. R. Tolkien. It was published in The Lost Road and Other Writings, volume V of The History of Middle-earth.
The Lhammas as published presents the theory that all the languages of Middle-earth descend from the language of the angelic beings or Valar, Valarin, and were divided in three branches:
Tolkien later revised this internal history. The Elves were said by Tolkien to have been able of inventing (constructing) their own language (see Primitive Quendian). Tolkien never wrote an 'updated' version of the Lhammas that would be coherent with this later internal history of the Elvish languages. The essay as it stands in The Lost Road can be thus seen as an interpolated manuscript, badly translated by Men in the Fourth Age or even later: "For many thousands of years have passed since the fall of Gondolin." (The Lhammas, p. 180). No autograph manuscripts of the Lhammas of Pengolodh were left; the three manuscripts we possess come from the original manuscript through an unknown number of intermediate copies.
The Lhammas was written in 1937. It exists in two versions, the shorter one being called the Lammasathen. Both are published, as edited by Christopher Tolkien, in The Lost Road.
The Lhammas and related writings like "The Etymologies" illustrate Tolkien's conception of the languages of Middle-earth as a language family analogous to Indo-European, with diverging branches and sub-branches — though for the immortal Elves the proto-language is remembered rather than reconstructed. This "concept of increasing separation" was also employed for the Sundering of the Elves in Tolkien's legendarium.