Basically in modern linguistics, language is analyzed on two basis, on the basis of structure and on the basis of usability. According to the variation of subjects language variation is essential. We can say it domain variation or functional variation. These variation is the variation of domain that is functional variation according to subject matter. On the basis of usability, the special language type which we use is called register. Linguistics have tried to capture these functional variations of the homogeneous code by introducing the concept of register or domain. The notion of register is based on the social fact – what people do with their language. In other words, it is a language variety used in social activity in a defined situation.
On the basis of register only we can differentiate between the functionality of language in different human practice. Basically to understand the speciality the concept of register came in linguistics. When we make differences in same language according to particular subject area then register is created. Due to the use only official Hindi is different from commercial Hindi, commercial Hindi is different from technical Hindi and technical Hindi is different from social Hindi and so on. All area have its own particular words and use. The glossaries and use of language in all areas are different. The identification of this difference is essential. We can see the difference in the following examples.
At the level of words: