Isogloss

Depending on the kind of linguistic feature mapped, more specific terms are sometimes used: • isophone – an isogloss for a phonetic or phonological feature • isolex – an isogloss for a lexical item • isomorph – an isogloss for a morphological feature • isoseme – an isogloss for a particular word meaning ==Methodology==

Because linguistic variation is often gradual, isoglosses are a cartographic abstraction: they summarize the distribution of a selected feature and may be drawn as approximate lines or treated as marking broader transition zones, depending on how the data are interpreted. ==Etymology==

The term isogloss (Ancient Greek ísos 'equal, similar' and glōssa 'tongue, dialect, language') is inspired by the iso- terminology of the natural sciences (such as isotherm and isobar), in which contour lines are used to represent equal values across space. ==Examples==

Centum–satem isogloss The centum–satem isogloss of the Indo-European language family relates to the different evolution of the dorsal consonants of Proto-Indo-European (PIE). In the standard reconstruction, three series of dorsals are recognised: In some branches (for example Greek, Italic and Germanic), the palatals merged with the velars: PIE "tremble (inwardly)" became Latin cupiō "desire" and "hundred" became Latin centum (pronounced [kentum]); but "interrogative pronoun" became quō "how? where?". They are known as centum branches, named after the Latin word for hundred. In other branches (for example, Balto-Slavic and Indo-Iranian), the labiovelars merged with the velars: PIE became Vedic Sanskrit kopáyati "shaken" and became Avestan kō "who?"; but became Avestan satəm. They are known as satem branches, after the Avestan word for hundred. Since the Balto-Slavic family, the Indo-Iranian family, and the other satem families are spoken in adjacent geographic regions, they can be grouped by an isogloss: a geographic line separating satem branches on one side from centum branches on the other. North–Midland isogloss (American English) A major isogloss in American English has been identified as the North–Midland isogloss, which demarcates numerous linguistic features, including the Northern Cities vowel shift: regions north of the line (including Western New York; Cleveland, Ohio; lower Michigan; northern Illinois; and eastern Wisconsin) have the shift, while regions south of the line (including Pennsylvania, central and southern Ohio, and most of Indiana) do not. Northwest Semitic A feature of the ancient Northwest Semitic languages is w becoming y at the beginning of a word. Thus, in Proto-Semitic and subsequent non-Northwest Semitic languages and dialects, the root letters for a word for "child" were w-l-d. However, in the ancient Northwest Semitic languages, the word was y-l-d, with w- > y-. Similarly, Proto-Semitic ā becomes ō in the Canaanite dialects of Northwest Semitic. Within the Aramaic languages and dialects of Northwest Semitic, the historic ā is preserved. Thus, an ancient Northwest Semitic language whose historic ā became ō can be classed as part of the Canaanite branch of Northwest Semitic. ==Isographs==

Just as there are distinguishing features of related languages, there are also distinguishing features of related scripts. For example, a distinguishing feature of the Iron Age Old Hebrew script is that the letters bet, dalet, ayin and resh do not have an open head, but contemporary Aramaic has open-headed forms. Similarly, the bet of Old Hebrew has a distinctive stance (it leans to the right), but the bet of the Aramaic and Phoenician scripts series has a different stance (in both, it leans to the left). In 2006, Christopher Rollston suggested using the term isograph to designate a feature of the script that distinguishes it from a related script series, such as a feature that distinguishes the script of Old Hebrew from Old Aramaic and Phoenician. ==See also==