Sindarin has a set of possessive pronouns that seem to be very similar to and possibly based on the forms of independent pronouns. Only a subset of the possible pronominal forms are attested, however. Examples include:

• 1st sg. nín “my”:
  • ae Adar nín i vi Menel “our [lit. my] Father who art in Heaven” (VT44/21).
  • ered en Echoriath, ered e·mbar nín “the mountains of Echoriath, the mountains of my home” (UT/40, 54).
• 1st pl. (exclusive) mín “our”:
  • anno ammen sír i mbas ilaurui vín “give us this day our (mín) daily bread” (VT44/21).
  • ar díheno ammen i úgerth vin “and forgive us our (mín) trespasses” (VT44/21).
• 2nd sg. polite lín “thy”:
  • no aer i eneth lín “hallowed be thy name” (VT44/21).
  • tolo i arnad lín “thy kingdom come” (VT44/21).
  • caro den i innas lin “thy will be done” (VT44/21).
• 3rd sg. tîn “his, *hers, its”:
  • ar Iorhael, Gelir, Cordof, ar Baravorn, ionnath dîn “and Frodo, Merry, Pippin and Hamfast his (tîn) sons” (SD/129).
  • ar Elanor, Meril, Glorfinniel, ar Eirien sellath dîn “and Elanor, Rose, Goldilocks and Daisy his (tîn) daughters” (SD/129).

Most of these examples are from a single source, Tolkien’s translation of Lord’s Prayer into Sindarin: Ae Adar Nín from the 1950s (VT44/21). Of interest are lín “thy” and mín “our”, which can be compared to attested le “you (polite)” and men “us”. Based on these, it seems the possessive pronoun is formed by (a) adding n to the independent pronoun and (b) lengthening the base vowel, with the caveat that the long ē became ī as was usual in Sindarin’s phonetic history. Assuming this pattern holds true universally, we can construct the following paradigm of possessive pronouns from the (somewhat hypothetical) paradigm of independent pronouns:

	Sg.	Pl.
1st person	nín “my”	mín “our”
2nd person familiar	*cín “your”
2nd person polite	lín “your (polite)”	*dín “your (pl.)”
3rd person	tín “his/her/its”	*tín “their”

Forms marked with a * are unattested, whereas mín and tín are attested only in the mutated forms vín and dîn. Tolkien’s marking of vowel length in Sindarin possessives is rather inconsistent. In Ae Adar Nín, he sometimes marked the vowel long (lín, vín) and sometimes did not (lin, vin). In the King’s Letter he marked the vowel as overlong (dîn) as was typical of Sindarin monosyllables, but elsewhere he marked it only as long (nín, lín, vín). In the table above I use í because that is more common among Tolkien’s examples, but many Neo-Sindarin writers use î instead.

It is conceivable that the Sindarin possessive pronouns are formed directly from object pronouns ending in n, but I think it is more likely they are derived from adjectival forms using the primitive adjective suffix ✶-nā such as *mēnā or *nīnā. They are probably analogues of Quenya independent possessive pronouns like menya or [ᴹQ.] ninya.

In all attested uses of the Sindarin possessive pronouns, they follow the noun and undergo soft mutation like adjectives. In most examples the noun itself also has a definite article. This resembles the use of the possessive pronoun in (older) Welsh, where the pronoun likewise follows the noun which usually has a definite article before it. This was discussed in A Welsh Grammar, Historical and Comparative (John Morris Jones, 1913, WGHC/282), a book Tolkien consulted frequently, which had Welsh examples like: y tŷ tau “(lit.) the house thy” (in modern Welsh you would say dy tŷ “your house”). This Welsh usage was most likely Tolkien’s inspiration for Sindarin possessives as pointed out by Bill Welden (VT44/24). Sindarin demonstrative pronouns use a similar construction.

There are several examples of possessive pronouns where the definite article is not present: Adar nín “my father”, ionnath dîn “his sons”, sellath dîn “his daughter”. In the first case, Adar is a vocative (indicating the person addressed) and hence cannot be definite, and in the other two cases the possessed noun follows a list of proper names which likewise are inherently definite. For purposes of Neo-Sindarin, I would generally mark the possessed noun with a definite article, just as is done when demonstrative pronouns are used as adjectives.

Reflexive Possessives: In the King’s Letter, there is a somewhat mysterious possessive pronoun în:

• ar e aníra ennas suilannad mhellyn în phain “and he desires to greet there all his friends” (SD/129).

This pronoun is doubly mysterious because elsewhere in the document, “his” is dîn (lenited tîn) as described above. One common theory is that în is a reflexive possessive pronoun “his own”, analogous to the reflexive pronoun im, but we have no further information on it.

Possessive Suffixes: In some notes written in 1957, Tolkien gave a complete paradigm of possessive suffixes based on the noun lam “tongue” (PE17/46), as an explanation of lammen “my tongue” from the phrase: fennas nogothrim, lasto beth lammen “doorway of the Dwarf-folk listen to the word of my tongue” (LotR/307; PE17/45). These possessive suffixes are unglossed, but their meanings can be deduced by comparison to the 1962 paradigm of subject suffixes (PE17/132) which they strongly resemble. The more archaic form of these suffixes are:

	Sg.	Pl.
1st person	-en “my”	-em(ir) “our”
1st person inclusive		-enc, -engir “our”
2nd person familiar	-eg “your”	-egir
2nd person polite	-el “your (polite)”	-elir “your (pl.)”
3rd person	-ed “his/her/its”	-ent “their”

Tolkien then gave their “later” forms as:

	Sg.	Pl.
1st person	-nin	-mein, -men
1st person inclusive		{-wein >>} -wen
2nd person familiar	{-gin >>} -gen	?
2nd person polite	-lein	?
3rd person	{-din >>} -dyn -deith -deid	?

These later possessive suffixes bear a striking resemblance to the known independent possessive pronouns, to the point where many of these suffixes may simply be the independent possessives as agglutinated suffixes. Also of interest is the preponderance of the diphthong ei, which may represent i-intrusion from more ancient suffixed adjectival forms, as in *-meny(a) > -menı̯ > -mein (vs. Q. menya). It is unfortunate that Tolkien did not include the later 2nd and 3rd person plural forms in this chart, but it is possible they were identical to the singular forms.

It is not clear whether these possessive suffixes coexisted with the independent possessives, but such possessive suffixes are attested elsewhere in Tolkien’s later writing, most notably in guren bêd enni “my heart (gûr-en) tells me” from the late 1960s (VT41/11). For Neo-Sindarin writing, the independent possessive forms are much more popular, especially since the suffixes introduce all kinds of issues with how final consonant and vowels might change in the suffixed forms, similar to the issues seen with the class plural suffix -ath. If nothing else, the variability in the later suffixed possessives hints that our rendition of independent possessives may be oversimplified. However, we currently don’t have enough information to make any relevant corrections.

Conceptual Development: We know something about the possessive form of Gnomish pronouns of the 1910s from a handful of examples appearing in the Gnomish Grammar and Gnomish Lexicon, notably irtha “her” (GG/11), ontha “his” (GL/62), [deleted] fintha “thine” (GL/35), and gwethra, possessive form of gwe- “you (pl.)” (GL/44). There is also thas, thath “thy” (GG/13), perhaps the beginning of a new conception (probably replacing fintha).

Unfortunately, after the 1910s there are no further possessive pronouns in the published corpus until the appearance of dîn “his” in the King’s Letter in 1948-49.