LANGUAGE VARIATION || SOCIOLINGUISTICS

 In this model  of language change and dialect differention, it should always be possible to relate any variation found within a language to the factors of time and distance alone. E.g. the  British and American varities, or English are separated by over two centuries of political independence and by the Atlantic ocean, Northumbrian and Cockney English are nearly 300 miles and any centuries apart.

Dialect  geographies have traditionaly attempted to produce their findings onmaps in what they call dialects atlases. They try to show the geographical boundaries of the distribution of a particular linguistics feature by drawing a line on a map. Such line is called an isoglosses. Alternatively, a particular area, a relic area, may show characteristic of being unaffected by changes spreading out from one or more neighboring areas. Very oftn the isoglosses for individual phonological features do not coincide with the one another to give us clearly demarcated dialects areas. Because dialects studies grew out of historical studies of language, it should also come as no surprise that they have focused almost exclusively on rural areas.

     Variation is an inharent characteristic of all language at all times and the pattern exhibited in this variation carry social meanings. The term linguistic variation( or simply variation ) refers to regional, social or contextual differences in the ways that a particular language is used. Variation between language, dialects, and speaker is known as intraspeaker variation. Variation within the language of a single speaker called intraspeaker variation. Since the rise of sociolinguistics in the 1960s. Interest in linguistics variation ( also called linguistics variability) has develop rapidly. All aspect of language. Including phonemes, morphemes, syntactic structure, and meanings are subject to variation.

SPEECH COMMUNITIES || SOCIOLINGUISTICS

Speech community is a term in sociolinguistics and linguistic anthropology for a group of people who use the same variety of a language and who share specific rules for speaking and for interpreting speech.
"In many ways," says George Yule, "speech is a form of social identity and is used, consciously or unconsciously, to indicate membership of different social groups or different speech communities" (The Study of Language, 2014).

People who speak the same language are not always members of the same speech community. On the one hand, speakers of South Asian English in India and Pakistan share a language with citizens of the U.S., but the respective varieties of English and the rules for speaking them are sufficiently distinct to assign the two populations to different speech communities. 
Most members of a society, even if they happen to live in the same town, belong to several speech communities. For example, an elderly person may have considerable difficulty following the monotonous chant of an auctioneer or comprehending what students talk about among themselves. But both the auctioneer and a college student can easily make the adjustment necessary to engage in a conversation with the elderly person and be fully understood; all they have to do is share enough characteristics of pronunciation, grammar, vocabulary, and manner of speaking to belong to the same speech community (Zdenek Salzmann, Language, Culture, and Society: An Introduction to Linguistic Anthropology. Westview, 2004) .

Conclusion

Language is a system, it means that languages is formed by patterned component permanently and can be verified. Language is also a tool that can be used to interact used by certain community each other. Speech communities can be happened between a group using same language and different language, with provision among them that is understanding each other.