In linguistics, code-switching occurs when a speaker alternates between two or more languages, or language varieties, in the context of a single conversation. 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 is distinct from other language contact phenomena, such as borrowing, pidgins and creoles, loan translation (calques), andlanguage transfer (language interference). Borrowing affects the lexicon, the words that make up a language, while code-switching takes place in individual utterances. Speakers form and establish a pidgin language when two or more speakers who do not speak a common language form an intermediate, third language. On the other hand, speakers practice code-switching when they are each fluent in both languages. Code mixing is a thematically related term, but the usage of the terms code-switching and code-mixing varies. Some scholars use either term to denote the same practice, while others apply code-mixing to denote the formal linguistic properties of language-contact phenomena, and code-switching to denote the actual, spoken usages by multilingual persons.
In the 1940s and 1950s, many scholars considered code-switching to be a sub-standard use of language. Since the 1980s, however, most scholars have come to regard it is a normal, natural product of bilingual and multilingual language use