The most widely used language in Middle-earth in the Third Age is Westron. Also known as the 'Common Speech'. All the Peoples save the Elves used it as their native tongue. At least this applies to those living within the bounds of the old kingdoms of Arnor and Gondor.
Languages spoken by the Elves
Far back in their history the Elves were divided into two main branches: The West-Elves (the Eldar) and the East-Elves. Three great tribes of the Eldar had sailed across the sea from Beleriand to the Valar and the language that evolved there was called Quenya. Quenya, also known as High-elven, can be regarded as elvish 'Latin'. The main alphabet used for writing Quenya was Tengwar which was invented by the Noldor and later greatly improved by Fëanor of the Noldor. Another alphabet used was Certar, also called Cirth. It was used mostly for scratched or incised inscriptions by the Sindar Elves in Beleriand. The other Eldarin tongue was Sindarin or Gray-elven. Gray-elven was originally akin to Quenya, it was the language of the Eldar who chose to remain in Beleriand as the Noldor, Teleri and the Vanyar sailed to Valinor. Because the Elves lived seperated from each other the two languages in time became quite different. Later, when the Exiled Elves led by Fëanor returned to the coasts of Beleriand, they adopted Sindarin for daily use, though Quenya was still used for ceremonies and other high occasions.
The languages used by Men
Westron was the tongue spoken by Men. This language dates back to the Edain, the 'Fathers of Men'. Edain is the elvish name for the human tribes who helped the Elves during the wars of Beleriand. The Edain were rewarded after the fall of The Dark Lord and received teaching, extended life-span and the island of Númenor. Those that chose to settle on the isle were named Dúnedain and they alone among Men could speak the elvish tongue Sindarin. Their forefathers had earlier come into contact with the Sindarin-speaking Elves. A few among Men also spoke Quenya. The common language of the Dúnedain however was their ancient language 'Adunaic'. The Men of Númenor established many settlements later on in their history along the western coasts of Middle-earth. Adunaic was spoken in these settlements and became intertwined with the language of 'lesser' men there. This mixed language became the Common Speech of those who had dealings with Númenor. When Númenor later was destroyed, Elendil and his heirs adopted the Common Speech and enriched it with many elvish words. In the north where most Men were descended from the Edain of the First Age, their language was related to the Adunaic. Take the Beornings as an example, or the Men of the Long Lake and of Dale. The Rohirrim spoke a tongue of their own, germanic sounding. Of course they also spoke Westron when necessary, at least the nobles among them did.
The Hobbits
The Hobbits spoke Westron, and had been doing so for at least a thousand years. They spoke it in a much less formal manner than the Men of, say Gondor. This is reflected in 'The Lord of the Rings'. The language in the book is quite archaic later on, as opposed to the first chapters. The Hobbits had always used the language of Men, not having a special language of their own. The Hobbits learned Westron upon arriving in Eriador. The Hobbits had fled from the dales of Anduin, close to Mirkwood. The language they had spoken there was akin to Rohirrim. This old language lingered on in many names and words. Many Hobbit words are thus similar to those of Rohan and Dale.
The Ents
The ancient Ents had a very special language, slow, repetitive and sonorous. It was impossible for others to learn their language. The Ents were deeply fond of learning tongues and especially loved Quenya, High-elven. The words used by 'Treebeard' and the other Ents were composed of elvish words strung together in Ent-fashion..
The Dwarves
The secretive Dwarves had a secret language, which they spoke among themselves. This was an ancient tongue which had seen little change over the years, a language of lore. Also the Dwarves had secret names, never revealed to those of other races. Gimli for instance never told anyone his real Dwarf name.
The Orcs and the Black Speech
The Orcs never had a completely original language, instead they took what they could from various languages and perverted the words into their own twisted and foul-sounding Black Speech. Sauron was the one who had devised this tongue. This language was very primitive, reflecting the primitive nature of the Orcs. Many dialects of this speech arose making it difficult for Orcs living far apart to understand each other. Because of this problem the Orcs of the Third Age spoke the universal Westron, at least its basics. A simple example of Black Speech is 'Snaga', meaning slave. The Uruk-hai often referred to the smaller orcs as 'Snaga'. After the first fall of Sauron the Black Speech was forgotten by all save the Nazgul. Later on, when Sauron returned to Mordor he reestablished it as the main language at his 'court', spoken by his officers and in Barad-dur. Westron remained the common speech of the ordinary Orcs. The inscription on the Ring is in Black Speech.
