Editing Comparative method (section)

===The Neogrammarian principle===
The foundation of the comparative method, and of comparative linguistics in general, is the [[Neogrammarian]]s' fundamental assumption that "sound laws have no exceptions". When it was initially proposed, critics of the Neogrammarians proposed an alternate position that summarised by the maxim "each word has its own history".<ref>{{harvnb|Szemerényi|1996|p=23}}.</ref> Several types of change actually alter words in irregular ways. Unless identified, they may hide or distort laws and cause false perceptions of relationship.

====Borrowing====
All languages [[loanword|borrow words]] from other languages in various contexts. Loanwords imitate the form of the donor language, as in Finnic ''kuningas'', from Proto-Germanic *''kuningaz'' ('king'), with possible adaptations to the local phonology, as in Japanese ''sakkā'', from English ''soccer''. At first sight, borrowed words may mislead the investigator into seeing a genetic relationship, although they can more easily be identified with information on the historical stages of both the donor and receiver languages. Inherently, words that were borrowed from a common source (such as English ''coffee'' and Basque ''kafe'', ultimately from Arabic ''qahwah'') do share a genetic relationship, although limited to the history of this word.

====Areal diffusion====
Borrowing on a larger scale occurs in [[areal feature (linguistics)|areal diffusion]], when features are adopted by contiguous languages over a geographical area. The borrowing may be [[Phonology|phonological]], [[Morpheme|morphological]] or [[Lexeme|lexical]]. A false proto-language over the area may be reconstructed for them or may be taken to be a third language serving as a source of diffused features.<ref>{{harvnb|Aikhenvald|2001|pp=2–3}}.</ref>

Several areal features and other influences may converge to form a [[Sprachbund]], a wider region sharing features that appear to be related but are diffusional. For instance, the [[Mainland Southeast Asia linguistic area]], before it was recognised, suggested several false classifications of such languages as [[Chinese language|Chinese]], [[Thai language|Thai]] and [[Vietnamese language|Vietnamese]].

====Random mutations====
Sporadic changes, such as irregular inflections, compounding and abbreviation, do not follow any laws. For example, the [[Spanish language|Spanish]] words ''palabra'' ('word'), ''peligro'' ('danger') and ''milagro'' ('miracle') would have been ''parabla'', ''periglo'', ''miraglo'' by regular sound changes from the Latin ''parabŏla'', ''perīcŭlum'' and ''mīrācŭlum'', but the ''r'' and ''l'' changed places by sporadic [[metathesis (linguistics)|metathesis]].<ref>{{harvnb|Campbell|2004|p=39}}.</ref>

====Analogy====
[[Analogy#Linguistics|Analogy]] is the sporadic change of a feature to be like another feature in the same or a different language. It may affect a single word or be generalized to an entire class of features, such as a verb paradigm. An example is the [[Russian language|Russian]] word for ''nine''. The word, by regular sound changes from [[Proto-Slavic]], should have been {{IPA|/nʲevʲatʲ/}}, but it is in fact {{IPA|/dʲevʲatʲ/}}. It is believed that the initial ''{{IPA|nʲ-}}'' changed to ''{{IPA|dʲ-}}'' under influence of the word for "ten" in Russian, {{IPA|/dʲesʲatʲ/}}.<ref>{{harvnb|Beekes|1995|p=79}}.</ref>

====Gradual application====
Those who study contemporary language changes, such as [[William Labov]], acknowledge that even a systematic sound change is applied at first inconsistently, with the percentage of its occurrence in a person's speech dependent on various social factors.<ref>{{harvnb|Beekes|1995|p=55}}; {{harvnb|Szemerényi|1996|p=3}}.</ref> The sound change seems to gradually spread in a process known as [[lexical diffusion]]. While it does not invalidate the Neogrammarians' axiom that "sound laws have no exceptions", the gradual application of the very sound laws shows that they do not always apply to all lexical items at the same time. Hock notes,<ref>{{harvnb|Hock|1991|pp=446–447}}.</ref> "While it probably is true in the long run every word has its own history, it is not justified to conclude as some linguists have, that therefore the Neogrammarian position on the nature of linguistic change is falsified".

====Non-inherited features====
The comparative method cannot recover aspects of a language that were not inherited in its daughter idioms. For instance, the [[Latin declension]] pattern was lost in [[Romance languages]], resulting in an impossibility to fully reconstruct such a feature via systematic comparison.{{Sfn|Meillet|1966|p=13}}