dialect, noun = a form of a language which is peculiar to a specific region or social group (from: Compact Oxford English Dictionary). Another definition, from Wikipedia, is “a complete system of verbal communication (oral or signed but not necessarily written) with its own vocabulary and/or grammar.”
Origin: from the Greek διάλεκτος (dialektos) – discourse, way of speaking.
Deciding whether a particular form of speech is a language or a dialect is a task fraught with difficulties. As well as linguistic criteria, there are also political, geographic and cultural issues to be considered. For example, closely related languages spoken in different countries, such as Norwegian, Swedish and Danish, might be considered dialects of one language if they were all spoken in a single country. There is considerable mutual intelligibility between these languages, but each of them has its own written standard, or two written standards in the case of Norwegian, which seems to be a good criterion for distinguishing languages. Perhaps you could define a language as a dialect with a standardised written form.
In the case of Arabic, there is one standard written form: Modern Standard Arabic, and many colloquial spoken forms, all of which are considered dialects of Arabic and are rarely used in writing. Though there is a high degree of mutual intelligibility between neighbouring colloquial forms of Arabic, for example, Jordanian and Syrian Arabic, speakers of these dialects have difficultly understanding the Arabic spoken by Moroccans and Algerians. This is an example of a dialect continuum.
Where do dialects come from?
When groups of people are isolated from others, the way they speak tends to drift away from mainstream forms of their language. Changes in the mainstream forms may not occur in the isolated form, and vice versa. Over time, the isolated form develops into a distinctive dialect, and if the isolation continues for long enough, that dialect may eventually become a language with it’s own written standard.
Another source of the differences between dialects comes from the languages once spoken in the regions where the dialects are now spoken. When people shift from one language to another, they usually carry over some features of their original language, including pronunciation, vocabulary and grammar. The dialects of English spoken in Ireland, for example, retain quite a few features of Irish. Similarly, substrates of the languages once spoken in the different regions of England can be found in some of today’s regional dialects. Moreover, the modern Celtic languages may contain substrates of the languages they replaced, whatever they were.
