Comparative method in the context of "Proto-Celtic language"

The Caucasian languages comprise a large and extremely varied array of languages spoken by more than ten million people in and around the Caucasus Mountains, which lie between the Black Sea and the Caspian Sea.

Linguistic comparison allows the classification of these languages into several language families, with little or no discernible affinity to each other. However, the languages of the Caucasus are sometimes mistakenly referred to as a family of languages. According to Asya Pereltsvaig, "grammatical differences between the three groups of languages are considerable. [...] These differences force the more conservative historical linguistics to treat the three language families of the Caucasus as unrelated."

Proto-Slavic (abbreviated PSl., PS.; also called Common Slavic or Common Slavonic) is the unattested, reconstructed proto-language of all Slavic languages. It represents Slavic speech approximately from the 2nd millennium BC through the 6th century AD. As with most other proto-languages, no attested writings have been found; scholars have reconstructed the language by applying the comparative method to all the attested Slavic languages and by taking into account other Indo-European languages.

Rapid development of Slavic speech occurred during the Proto-Slavic period, coinciding with the massive expansion of the Slavic-speaking area. Dialectal differentiation occurred early on during this period, but overall linguistic unity and mutual intelligibility continued for several centuries, into the 10th century or later. During this period, many sound changes diffused across the entire area, often uniformly. This makes it inconvenient to maintain the traditional definition of a proto-language as the latest reconstructable common ancestor of a language group, with no dialectal differentiation. (This would necessitate treating all pan-Slavic changes after the 6th century or so as part of the separate histories of the various daughter languages.) Instead, Slavicists typically handle the entire period of dialectally differentiated linguistic unity as Common Slavic.

Proto-Armenian is the earlier, unattested stage of the Armenian language which has been reconstructed by linguists. As Armenian is the only known language of its branch of the Indo-European languages, the comparative method cannot be used to reconstruct its earlier stages. Instead, a combination of internal and external reconstruction, by reconstructions of Proto-Indo-European and other branches, has allowed linguists to piece together the earlier history of Armenian.

In the tree model of historical linguistics, a proto-language is a postulated ancestral language from which a number of attested languages are believed to have descended by evolution, forming a language family. Proto-languages are usually unattested, or partially attested at best. They are reconstructed by way of the comparative method.

In the family tree metaphor, a proto-language can be called a mother language. Occasionally, the German term Ursprache (pronounced [ˈuːɐ̯ʃpʁaːxə] ; from ur- 'primordial, original' + Sprache 'language') is used instead. It is also sometimes called the common or primitive form of a language (e.g. Common Germanic, Primitive Norse).

The Balto-Slavic languages form a branch of the Indo-European family of languages, traditionally comprising the Baltic and Slavic languages. Baltic and Slavic languages share several linguistic traits not found in any other Indo-European branch, which points to a period of common development and origin.

A Proto-Balto-Slavic language is reconstructable by the comparative method, descending from Proto-Indo-European by means of well-defined sound laws, and from which modern Slavic and Baltic languages descended. One particularly innovative dialect separated from the Balto-Slavic dialect continuum and became ancestral to the Proto-Slavic language, from which all Slavic languages descended.

Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. No direct record of Proto-Indo-European has been discovered; its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. Far more work has gone into reconstructing PIE than any other proto-language, and it is the best understood of all proto-languages of its age. The majority of linguistic work during the 19th century was devoted to the reconstruction of PIE and its daughter languages, and many of the modern techniques of linguistic reconstruction (such as the comparative method) were developed as a result.

PIE is hypothesized to have been spoken as a single language from approximately 4500 BCE to 2500 BCE during the Late Neolithic to Early Bronze Age, though estimates vary by more than a thousand years. According to the prevailing Kurgan hypothesis, the original homeland of the Proto-Indo-Europeans may have been in the Pontic–Caspian steppe of eastern Europe. The linguistic reconstruction of PIE has provided insight into the pastoral culture and patriarchal religion of its speakers. As speakers of Proto-Indo-European became isolated from each other through the Indo-European migrations, the regional dialects of Proto-Indo-European spoken by the various groups diverged, as each dialect underwent shifts in pronunciation (the Indo-European sound laws), morphology, and vocabulary. Over many centuries, these dialects transformed into the known ancient Indo-European languages. From there, further linguistic divergence led to the evolution of their current descendants, the modern Indo-European languages.

In historical linguistics, cognates or lexical cognates are sets of words that have been inherited in direct descent from an etymological ancestor in a common parent language.

Because language change can have radical effects on both the sound and the meaning of a word, cognates may not be obvious, and it often takes rigorous study of historical sources and the application of the comparative method to establish whether lexemes are cognate. It can also happen that words which appear similar, or identical, in different languages, are not cognate.

The Divine Twins are youthful horsemen, either gods or demigods, who serve as rescuers and healers in Proto-Indo-European mythology.

Like other Proto-Indo-European divinities, the Divine Twins are not directly attested by archaeological or written materials, but scholars of comparative mythology and Indo-European studies generally agree on the motifs they have reconstructed by way of the comparative method.