DISCLAIMER: This article is preliminary research on the part of its author (Paul Strack) and does not necessarily reflect the opinions of the owner of this site. Since the source material is complex and its interpretation can be subjective, multiple conclusions are possible.
Like Quenya, Sindarin once had a dual inflection, used for pairs of objects, but in Sindarin this dual has fallen out of use:
The S. duals of nouns or pronouns early became obsolete, except in written works. A case occurs in Orgalaðad “Day of the Two Trees”, but since these S. nouns were all derived from Quenya names of the 6-day week, brought from Valinor, it may be due to an attempt to imitate Q. duals, such as ciriat 2 ships. In any case -d was later lost, and so we have argonath “the group of (two) noble stones” instead of *argonad (1972 letter to Richard Jeffery, Let/427).
This Sindarin dual was derived from ✶ata the “numerative dual ending”. The other ancient (and more common) dual ending was ✶-ū, but since final vowels vanished in Sindarin this u-dual vanished completely and there are only remnants of it in fossilized forms like the plural (really a dual) of lheweg “ear”:
- *slasū > lhahu > lhau, spelled lhaw “ears” (PE17/62, 77; Ety/LAS²).
There are several clear -ad duals attested in Sindarin, however:
- Orgaladhad “Day of Two Trees (galadh)” (LotR/1110).
- samarad “*two neighbors (sammar)” (VT48/20).
- nobad “thumb and index finger as a pair, (lit.) *pickers” (VT48/5).
It is conceivable that the -ad dual remained active into the First Age (when names like Orgaladhad were introduced) and only fell out of use by the Third Age.
Conceptual Development: Tolkien mentioned an archaic dual form in the Gnomish Grammar of the 1910s that used the dual suffix -wi:
Nouns only preserve in living forms singular and plural. Traces occur of the commonest old duals but these are now confined to such as: … mabwi “(a pair of) hands” … talwi “feet” … hent [or] henwi “eyes” … hethwi “brother and sister” … hunt (old -nt ending) “the nose (originally nostrils)”. Dual -wi, -wint, -wid [nominative, genitive, dative]. Adjectives follow in singular but without mutation (GG/10-11).
Signs of both the -wi/-ui and the -(n)t dual suffixes can also be seen in declension charts appearing in Gnomish Lexicon Slips (addendums to the Gnomish Lexicon) written towards the end of the 1910s (PE13/117-118):
- engant dual of engan “spear”.
- ceralt dual of ceral “jar”.
- golui dual of gôl “gnome”.
- gui(w) dual of gweg “man”.
Some dual forms are also mentioned in the Early Noldorin Grammar of the 1920s and follow roughly the same patterns:
- badui dual of ᴱN. bad “way” (PE13/120).
- [deleted] *duilent dual of ᴱN. duilen “swallow” (PE13/120 note #4, give in mutated from nuilent).
- him dual of ᴱN. hen(n) “eye” (PE13/122, replacing deleted henu).
There is also a remnant of the -(n)t dual in The Etymologies of the 1930s: the dual hent for N. hên “eye” (EtyAC/KHEN-D-E).