Areal feature in the context of "Geolinguistics"

Hakka (Chinese: 客家话; pinyin: Kèjiāhuà; Pha̍k-fa-sṳ: Hak-kâ-va / Hak-kâ-fa, Chinese: 客家语; pinyin: Kèjiāyǔ; Pha̍k-fa-sṳ: Hak-kâ-ngî) forms a language group of varieties of Chinese, spoken natively by the Hakka people in parts of Southern China, Taiwan, some diaspora areas of Southeast Asia and in overseas Chinese communities around the world.

Due to its primary usage in isolated regions where communication is limited to the local area, Hakka has developed numerous varieties or dialects, spoken in different provinces, such as Guangdong, Guangxi, Hainan, Fujian, Sichuan, Hunan, Jiangxi, Guizhou, as well as in Taiwan, Singapore, Malaysia, Thailand and Indonesia. Hakka is not mutually intelligible with Yue, Wu, Min, Mandarin or other branches of Chinese, and itself contains a few mutually unintelligible varieties. It is most closely related to Gan and is sometimes classified as a variety of Gan, with a few northern Hakka varieties even being partially mutually intelligible with southern Gan. There is also a possibility that the similarities are just a result of shared areal features.

The Balkan sprachbund or Balkan language area is an ensemble of areal features—similarities in grammar, syntax, vocabulary and phonology—among the languages of the Balkans. Several features are found across these languages though not all apply to every single language. The Balkan sprachbund is a prominent example of the sprachbund concept.

The languages of the Balkan sprachbund share their similarities despite belonging to various separate language family (genetic) branches. The Slavic, Hellenic, Romance and Albanian branches all belong to the large Indo-European family, and the Turkish language is non-Indo-European.

A sprachbund (/ˈsprɑːkbʊnd/ SPRAHK-buund, from German: Sprachbund [ˈʃpʁaːxbʊnt] , lit. 'language federation'; pl. sprachbünde or sprachbunds), also known as a linguistic area, area of linguistic convergence, or diffusion area, is a group of languages that share areal features resulting from geographical proximity and language contact. The languages may be genetically unrelated, or only distantly related, but the sprachbund characteristics might give a false appearance of relatedness.

A grouping of languages that share features can only be defined as a sprachbund if the features are shared for some reason other than the genetic history of the languages. Without knowledge of the history of a regional group of similar languages, it may be difficult to determine whether sharing indicates a language family or a sprachbund.

As the Proto-Indo-European language (PIE) broke up, its sound system diverged as well, as evidenced in various sound laws associated with the daughter Indo-European languages.Especially notable is the palatalization that produced the satem languages, along with the associated ruki sound law. Other notable changes include:

• Grimm's law and Verner's law in Proto-Germanic
• an independent change similar to Grimm's law in Armenian, dubbed the Armenian Consonant Shift
• Adjarian's law in Proto-Armenian
• loss of prevocalic *p- in Proto-Celtic
• Brugmann's law in Proto-Indo-Iranian
• Winter's law and Hirt's law in Balto-Slavic
• merging of voiced and breathy-voiced stops, and /a/ and /o/, in various "northern" languages
• Sturtevant's law
• Cowgill's laws of Germanic and Greek
• Osthoff's law
• Slavic first, second and third ("progressive") palatalization

Bartholomae's law in Indo-Iranian, and Sievers's law in Proto-Germanic and (to some extent) various other branches, may or may not have been common Indo-European features. A number of innovations, both phonological and morphological, represent areal features common to the Italic and Celtic languages; among them the development of labiovelars to labial consonants in some Italic and Celtic branches, producing "p-Celtic" and "q-Celtic" languages (likewise "p-Italic" and "q-Italic", although these terms are less used). Another grouping with many shared areal innovations comprises Greek, Indo-Iranian, and Armenian; among its common phonological innovations are Grassmann's law in Greek and Indo-Iranian, and weakening of pre-vocalic /s/ to /h/ in Greek, Iranian and Armenian.

In historical linguistics, the wave model or wave theory (German: Wellentheorie) is a model of language change in which a new language feature (innovation) or a new combination of language features spreads from its region of origin, being adopted by a gradually expanding cluster of dialects. Each innovation starts at a certain place, and spreads from speaker to speaker, from dialect to dialect, in the same fashion as waves on the water.

The theory was intended as a substitute for the tree model, which did not seem to be able to explain the existence of some features, especially in the Germanic languages, by descent from a proto-language. At its most ambitious, it is a wholesale replacement for the tree model of languages. During the 20th century, the wave model had little acceptance as a model for language change overall, except for certain cases, such as the study of dialect continua and areal phenomena; it has recently gained more popularity among historical linguists, due to the shortcomings of the tree model.

Languages of the Indo-European family are classified as either centum languages or satem languages according to how the dorsal consonants (sounds of "K", "G" and "Y" type) of the reconstructed Proto-Indo-European language (PIE) developed. An example of the different developments is provided by the words for "hundred" found in the early attested Indo-European languages (which is where the two branches get their names). In centum languages, they typically began with a /k/ sound (Latin centum was pronounced with initial /k/), but in satem languages, they often began with /s/ (the example satem comes from the Avestan language of Zoroastrian scripture).

The table below shows the traditional reconstruction of the PIE dorsal consonants, with three series, but according to some more recent theories there may actually have been only two series or three series with different pronunciations from those traditionally ascribed. In centum languages, the palatovelars, which included the initial consonant of the "hundred" root, merged with the plain velars. In satem languages, they remained distinct, and the labiovelars merged with the plain velars.

Relational nouns, or relator nouns, are a word class in many languages. They are characterized as functioning syntactically as nouns although they convey the meaning for which other languages use adpositions (prepositions and postpositions). In Mesoamerican languages, the use of relational nouns constitutes an areal feature of the Mesoamerican linguistic area, including the Mayan languages, Mixe–Zoquean languages, and Oto-Manguean languages.

Relational nouns are also widespread in Southeast Asia (e.g. Vietnamese, Thai), East Asia (e.g. Mandarin Chinese, Japanese, Lhasa Tibetan), Central Asia (e.g. the Turkic languages), Armenian, the Munda languages of South Asia (e.g. Sora), and in the Micronesian languages.