Language is a form of social and cultural interaction in society. In this interaction, language is understood from two aspects, namely aspects of form and meaning. If these two aspects can be understood, language can be interpreted as a series of signs that contain the context of meaning and value. Interaction can be intended more specifically, namely interaction in language learning in the learning room and interaction of students outside the learning room as an application of language learning. Students are expected to be able to communicate in a society that has a context of meaning and value in every language spoken. Therefore, the ability of students to speak properly and correctly will be realized if it is supported by the sociolinguistic competence of the language teacher and the students themselves. Sociolinguistics is a scientific discipline that has an object of study on the relationship between language and society. Sociolinguistics also pays attention to the conditions of society that affect the use of language.
The contribution of sociolinguistics in language teaching can be seen from the determination of the language of instruction to be used in the learning process. The ability of language teachers to choose variations is determined by their sociolinguistic competence. These competencies lead to using language that is familiar to students according to the situation. In sociolinguistics it is known as code switching and code mixing. This is done solely to create communicative learning.
Indonesian language teaching must be able to place language as a means of delivering information, carrying out social processes, and interacting in the learning process. In Fishman's formulation (Chaer and Agustina, 2010: 48), sociolinguistics explains the use of language in certain social aspects or aspects by paying attention to "who speaks, what language, to whom, when, and to what end". The Fishman formulation is considered important to be used as a guide in interacting. The formulation invites to consider several things in language, namely who is speaking, what language should be used, and for whom the language is used.
One application of sociolinguistics in accordance with the above formulation is about the use of personal pronouns in language. A language teacher should be able to explain to students about the social rules of using personal pronouns. Without the help of sociolinguistic explanations, students will find it difficult to use personal pronouns according to social rules. The social rules include, to whom, when, and where the pronoun should be used.
In addition, language teaching must also be able to identify language errors or interference caused by widespread slang. A sociolinguistic explanation of the interference of a language is more appropriate to use to base the identification. Given that there are many interferences of foreign terms that replace words to make them look cool and slang.
