Historical background
In the phonological development of Sindarin, lenition refers (primarily) to the mutation of medial consonants, occurring usually between two vowels (VCV). It affected the Old Sindarin sounds p, t, k, b, d, g, m and s.
More specifically, the evolution of these sounds can be visualized in these examples:
- p > b
- OS *kelepe > S celeb "silver"
- t > d
- OS *atar > S adar "father"
- k > g
- OS beleka > S beleg "great"
- b > v
- OS *jabasse > S Iavas "autumn"[note 1]
- d > dh
- OS *edelo > S Edhel "Elf"
- g > ∅
- OS *khugo > *huȝo[note 2] > S hû "dog"[note 1]
 In compounds
As a consequence, this process took place also in Old Sindarin compounds, when the initial letter of a word was no longer initial in a compound. Even in later compounds that would be pure Sindarin, the lenition was solidified as a rule, envisioning retroactively the lenition process from a theoretical Old Sindarin compound.
For example the word athrabeth "debate, converse (lit. 'across-word')" can be analyzed both as a derivative of OS word *athrapettha but also as a compound of Sindarin words athra- "across" + peth "word".
The fact that the above sounds mutated when medially was solidified as a rule
- thind + coll > Thingol (< ?OS *Thindakollo)
- cair + tân > Cirdan (< ?OS *Kiriatâno)
- fanui + dol > Fanuidhol (< ?OS *Fanoidolo)
- Edhel + sarn > Edhelharn (< ?OS *Edelosarno)
- har- + Gondor > Harondor (< ?OS *Kharagonddor)
- ar- + gwend > Arwen (< ?OS *Arwende; no g would evolve between ar- and wende)
- or- + hall > orchal (< ?OS *orkhalna; kh would not lenite as h inside a word)
 Grammatical and Syntactical significance
This article or section is a stub. Please help Tolkien Gateway by expanding it.
- Mutations in Sindarin by Thorsten Renk; it also covers Lenition.
- Soft mutation from the Ardalambion article on Sindarin by Helge Fauskanger
- Some Questions on Sindarin Lenition by Alfred W. Tueting