switching

In linguistics, code-switching or language alternation occurs when a speaker alternates between two or more languages, or language varieties, in the context of a single conversation or situation.
Code-switching is different from plurilingualism in that plurilingualism refers to the ability of an individual to use multiple languages, while code-switching is the act of using multiple languages together. Multilinguals (speakers of more than one language) sometimes use elements of multiple languages when conversing with each other. Thus, code-switching is the use of more than one linguistic variety in a manner consistent with the syntax and phonology of each variety.
Code-switching may happen between sentences, sentence fragments, words, or individual morphemes (in synthetic languages). However, some linguists consider the borrowing of words or morphemes from another language to be different from other types of code-switching.
Code-switching can occur when there is a change in the environment in which one is speaking, or in the context of speaking a different language or switching the verbiage to match that of the audience. There are many ways in which code-switching is employed, such as when speakers are unable to express themselves adequately in a single language or to signal an attitude towards something. Several theories have been developed to explain the reasoning behind code-switching from sociological and linguistic perspectives.

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