3. Comparative method of linguistic research.

In linguistics, the comparative method is a technique for studying the development of languages by performing a feature-by-feature comparison of two or more languages with common descent from a shared ancestor, as opposed to the method ofinternal reconstruction, which analyzes the internal development of a single language over time.^[1] Ordinarily both methods are used together to reconstruct prehistoric phases of languages, to fill in gaps in the historical record of a language, to discover the development of phonological, morphological, and other linguistic systems, and to confirm or refute hypothesized relationships between languages.

The comparative method was developed over the 19th century. Key contributions were made by the Danish scholars Rasmus Rask and Karl Verner and the German scholar Jacob Grimm. The first linguist to offer reconstructed forms from a proto-languagewas August Schleicher, in his Compendium der vergleichenden Grammatik der indogermanischen Sprachen, originally published in 1861.^[2] Here is Schleicher’s explanation of why he offered reconstructed forms.

The comparative method aims to prove that two or more historically attested languages are descended from a single proto-language by comparing lists of cognate terms. From them, regular sound correspondences between the languages are established, and a sequence of regular sound changes can then be postulated, which allows the proto-language to be reconstructed. Relation is deemed certain only if at least a partial reconstruction of the common ancestor is feasible, and if regular sound correspondences can be established with chance similarities ruled out.

4. The first vowel shift Grimm’s Law.

Grimm's law (also known as the First Germanic Sound Shift or the Rask's rule), named after Jacob Grimm, is a set of statements describing the inherited Proto-Indo-European (PIE) stop consonants as they developed in Proto-Germanic (the common ancestor of theGermanic branch of the Indo-European family) in the 1st millennium BC. It establishes a set of regular correspondences between earlyGermanic stops and fricatives and the stop consonants of certain other centum Indo-European languages (Grimm used mostly Latinand Greek for illustration). Grimm's law consists of three parts, which must be thought of as three consecutive phases in the sense of achain shift:^[1]

1. Proto-Indo-European voiceless stops change into voiceless fricatives.

2. Proto-Indo-European voiced stops become voiceless stops.

3. Proto-Indo-European voiced aspirated stops become voiced stops or fricatives (as allophones).

The chain shift can be abstractly represented as:

bʰ → b → p → ɸ

dʰ → d → t → θ

gʰ → g → k → x

gʷʰ → gʷ → kʷ → xʷ

Here each sound moves one position to the right to take on its new sound value. Notice that the new sound value entails the loss of a feature at each of the three steps. First the aspiration feature is lost, then voice and finally stop leaving a continuant.

The voiced aspirated stops may have first become voiced fricatives before hardening to the voiced unaspirated stops "b", "d", and "g" under certain conditions; however, some linguists dispute this. See Proto-Germanic phonology.

Grimm's law was the first non-trivial systematic sound change to be discovered in linguistics; its formulation was a turning point in the development of linguistics, enabling the introduction of a rigorous methodology to historical linguistic research. The correspondences between Latin p and Germanic f was first noted by Friedrich von Schlegel in 1806. In 1818 Rasmus Christian Rask elaborated the set of correspondences to include other Indo-European languages such as Sanskrit and Greek, and the full range of consonants involved. In 1822 Jacob Grimm, the elder of the Brothers Grimm, in his book Deutsche Grammatik, formulated the law as a general rule (and extended to include standard German).

5. Verner's law, stated by Karl Verner in 1875, describes a historical sound change in the proto-Germanic language whereby voiceless fricatives *f, *T, *s and *x, when immediately following an unstressed syllable in the same word, underwent voicing and became respectively *b, *d, *z and *g.

Karl Verner was the first scholar who put his finger on the factor governing the distribution of the two outcomes. He observed that the apparently unexpected voicing of voiceless fricatives (and their falling together with *b, *d, *g) occurred if they were non-initial and immediately preceded by a syllable that carried no stress in PIE. The original location of stress was often retained in Greek and early Sanskrit, though in Germanic stress eventually became fixed on the initial (root) syllable of all words. The crucial diference between *pAte:r and *bhra:te:r was therefore one of second-syllable versus first-syllable stress (cf. Sanskrit pitá: versus bhrá:ta:).

The *werT- | *wurd- contrast is likewise explained as due to stress on the root versus stress on the inflectional suffix (leaving the first syllable unstressed). There are also other Vernerian alternations such as illustrated by Modern German ziehen | (ge)zogen 'draw' < PGmc. *tiux- | *tug- < PIE *déuk- | *duk- 'lead'.

There is a spinoff from Verner's Law: the rule accounts also for PGmc *z as the development of PIE *s in some words. Since this *z changed to *r in the Scandinavian languages and in West Germanic (German, Dutch, English, Frisian), Verner's Law resulted in the alternation /s/ versus /r/ in some inflectional paradigms. For example, the Old English verb ceosan 'choose' had the past plural form curon and the past participle (ge)coren < *kius- | *kuz- < *g^éus- | *g^us- 'taste, try'. We would have coren forchosen in Modern English if the consonantal shell of choose and chose had not been generalised. But Vernerian /r/ has not been levelled out in were < PGmc. *we:z-, related to was. Similarly, lose, though it has the weak form lost, also has the compound form forlorn.

It is worth noting that the Verner's Law comes chronologically after Grimm's Law (because Grimm's Law provides most of its input) and before the Germanic shift of stress to the initial syllable (because the voicing is conditioned by the old location of stress). The stress shift erased the conditioning environment and made the Vernerian variation between voiceless fricatives and their voiced alternants look mysteriously haphazard.

The moral of Verner's Law is that crucial evidence necessary to sort out the historical evolution of a linguistic lineage may reside where few people would dream of looking for it. Verner found it "out there" in Greek and Sanskrit, while everyone else had tacitly assumed that Germanic changes can be explained in Germanic terms without recourse to external comparison.