These languages are distinguished somewhat along phonological lines, that is, languages which apparently differ in their forms are distinguished, while those which do not are grouped together. My analysis is based in some respects on studies of the languages rather than being entirely dependent on the published statements of J.R.R. Tolkien. I have tried to speak carefully and not say more than is known. Comments would be much appreciated.

I would like to offer an explanation for two terms that I use for the levels of language use. The others are used and defined by Tolkien. A "house language" is a language which is used in a family or household but which is not the common speech of the larger community. A "private language" may well be the high speech of a certain people, but it is considered too holy or too powerful for public or everyday use.

Before the 1st Age:

Common Elvish may be the name for the language spoken by Elves when they first awoke in the Great Lands and before they reached Valinor. It is little attested but much can be inferred about it based on the information given. Proto-Eldarin is a name for it as a reconstructed form.

Valarian is the language of the Valar in Valinor. It is not attested but it is said to have affected the speech of the Elves once they arrived in Valinor.

Eldarin may be said to include various languages spoken by Elves in Valinor, such as Lindarin, Ingwiqendya, and Valinorean Quenya which differ from standard Quenya in some way (although the word Eldarin is also applied to any language spoken by the Noldor). It is not clear exactly what is meant by these names, nor how the languages relate to each other. Some additional languages named and there are several attested examples of words in some of the languages named.

Quenya is spoken by the Elves of Valinor before the 1st Age and remains a language of high speech or a book language almost everywhere through the Third Age.

Telerin is spoken before the 1st Age by the Elves of Alqualonde in Valinor, and may continue to be spoken indefinitely there and by Ciirdan at the Grey Havens.

Old Noldorin is presumably spoken before the 1st Age, either by the Noldor of Valinor, or by the Ilkorins of Beleriand, and it may continue in use thereafter.

First Age

Quenya is spoken in Beleriand in the 1st Age, and although banned by Thingol remains as a house language of the Noldor and becomes the first language of some of the Edain.

The Ilkorin Dialects are spoken by Ilkorin Elves in Beleriand in the 1st Age and include:

Ilkorin, the blanket name for all these dialects
Doriathrin, specifically that form spoken at Menegroth
Danian, also called Ossiriandeb which is spoken by the Green-elves of Ossiriand (see also Nandorin of the 2nd Age and Silvan in the 3rd Age)
Falassian, spoken by the Elves of the Falas at Brithombar, Eglorest and possibly at the mouths of Sirion

Noldorin is spoken by the Noldor of the 1st Age in Beleriand, and it is closely related to the Ilkorin dialects. There are 5 dialects not differentiated phonologically but described:

1) of Mithrim (of Fingolfin's folk)
2) of Nargothrond (of Finrod Felagund's folk)
3) of Gondolin (of Turgon's folk)
4) of the sons of Feanor and their followers
5) muulanoldorin, or thrall Gnomish

Dialects of the Lembi and other Dark Elves in Beleriand and eastwards are named but not attested.

Taliska is the usual language of the three houses of the Edain in Beleriand in the 1st Age, but it is superseded by Noldorin or Quenya among most of them. It is most likely also spoken by Dwarves in the 1st Age.

Dwarvish of the Petty Dwarves is slightly attested in Beleriand in the 1st Age.

Orkish is attested in Beleriand in the 1st Age, although most Orcs carry Sindarin names, at least among the Elves.

2nd Age

Qenya of the 2nd Age is spoken in Tol Eressea by the returning Noldor and may continue in use indefinitely.

Quenya of the 2nd Age is used as a high speech in Nuumenor [which I call Nuumenorean Quenya]. It is also probably a high speech of Gil-galad and other Noldorin Elves on the coast of Middle-earth; of Celebrimbor and the Noldor of Eregion; of Elrond and his household at Rivendell; and of Galadriel in Lothloorien.

Gnomish or Goldogrin is spoken in the 2nd Age and following, in Tol Eressea by the Noldor returning there. It seems to be influenced by and includes many words from the Ilkorin dialects.

Sindarin is spoken in the 2nd and 3rd Ages of Middle-earth. It is closely related to Noldorin. It was the usual language of the Noldor of Eregion, the folk of Elrond's house and of the Duunedain, both in Nuumenor before it's fall and in their kingdoms in exile in the north and south of Middle-earth. Sindarin is also commonly spoken by Dwarves in the 2nd Age, especially in Moria.

Nandorin is the language spoken in the 2nd Age by the Green-elves east of the Misty Mountains.

Aduunaic is spoken in Nuumenor during the 2nd Age, especially among the less educated or descendants of certain groups. It appears to have a number of dialects and variations. It was introduced back into Middle-earth before the destruction of Nuumenor (though speakers of a related language had remained in Middle-earth in the meantime). It is the source of the many dialects known as Westron spoken at Umbar, Tharbad and Gondor and points in between.

Black Speech, as spoken by Sauron, is attested from Eregion early in the 2nd Age.

3rd Age

Quenya of the 3rd Age is used as a high speech among Elves along the western coast and in Rivendell and Loorien, and remains in use among the Duunedain, and among certain educated Hobbits.

Entish Quenya, as it is spoken in the 3rd Age, (and presumably long before) may be considered a dialect of Quenya, because it has so many words of Quenya in it. The Ents also had a language unique to the, which no one else could learn. Fangorn also knew Westron and perhaps Sindarin or Ilkorin.

Sindarin continues to be spoken in the 3rd Age in Middle-earth. It is the usual speech of the folk of Elrond's house and of the Duunedain in both Gondor and the north of Middle-earth and it may be the house language of Thranduil of Mirkwood.

Silvan dialects in the 3rd Age are spoken by the Elves of Loorien and Mirkwood; the speech of the Elves of Mirkwood is called a Woodland dialect.

Westron is the common speech of mortals in the 3rd Age and dialects are spoken among the folk of Gondor, Bree, and other places. Specific dialects (usually given in Germanicized form) are:

Rohannish of the Rohirrim (with both the current and an older form alluded to); and Hobbitish of the Hobbits, of both the Shire and the Stoors.

Additional languages by mortals ascribed to the 3rd Age which are but poorly attested include:

Pre-Nuumenoorean, which actually predates the reintroduction of Westron; most examples are from the area around the Ered Nimrais; The language of the Dunlendings, east and south of the Misty Mountains; The language of the Haradrim, from far south of Gondor; and Druug, which is attested from the 1st Age as well as the 3rd Age generally around the area of the Ered Nimrais. As it is also said that there were Druugs in Nuumenor, it may be thought to have been spoken there as well.

Dwarvish also called Khuzdul is not easy to date, but words are known from the 1st Age in Beleriand and from the 3rd Age by Dwarves of the Longbeards in Middle-earth at many sites. It is a private language and is not thought to be known by anyone other than Dwarves, except for Gandalf.

Orkish or Debased Black speech is attested from the 3rd Age among several groups of orcs including those of Moria, Isengard and Mordor. It is said to have many mutually unintelligible dialects, although they are not delineated.