Code-switching can occur between sentences (inter-sentential) or within a single sentence (intra-sentential). Code-switching within a sentence tends to occur more often at points where the syntax of the two languages align; thus it is uncommon to switch from English to French after an adjective and before a noun, because a French noun normally "expects" its adjectives to follow it. It is, however, often the case that even unrelated languages can be "aligned" at the boundary of a relative clause or other sentence sub-structure.
Although some commentators have seen code-switching as reflecting a lack of language ability, most contemporary scholars consider code-switching to be a normal and natural product of interaction between the bilingual (or multilingual) speaker's languages.
Code-switching can be distinguished from other language contact phenomena such as loan translation (calques), borrowing, pidgins and creoles, and transfer or interference.
There are different perspectives on code-switching. A major approach in sociolinguistics focuses on the social motivations for switching, a line of inquiry concentrating both on immediate discourse factors such as lexical need and the topic and setting of the discussion, and on more distant factors such as speaker or group identity, and relationship-building (solidarity). Code-switching may also be reflective of the frequency with which an individual uses particular expressions from one or the other language in his/her daily communications; thus, an expression from one language may more readily come to mind than the equivalent expression in the other language.
A second perspective primarily concerns syntactic constraints on switching. This is a line of inquiry that has postulated grammatical rules and specific syntactic boundaries for where a switch may occur.
While code-switching had previously been investigated as a matter of peripheral importance within the more narrow tradition of research on bilingualism, it has now moved into a more general focus of interest for sociolinguists, psycholinguists and general linguists.
Code-switching can be related to and indicative of group membership in particular types of bilingual speech communities, such that the regularities of the alternating use of two or more languages within one conversation may vary to a considerable degree between speech communities. Intra-sentential code-switching, where it occurs, may be constrained by syntactic and morpho-syntactic factors which may or may not be universal in nature.
People code-switch for a number of reasons:
- Code-switching a word or phrase from language-B into language-A can be more convenient than waiting for one's mind to think of an appropriate language-B word.
- Code-switching can help an ethnic minority community retain a sense of cultural identity, in much the same way that slang is used to give a group of people a sense of identity and belonging, and to differentiate themselves from society at large.
- Code-switching is a common means to shift footing or contextualization.
Types of code switching:
- "Intersentential switching" is switching outside the sentence or clause level, for example at sentence or clause boundaries.
- "Intra-sentential switching" is switching within a sentence or clause.
- "Tag-switching is switching" a tag phrase or word from language B into language A. (This is a common intra-sentential switch.)
- "Intra-word switching" is switching within a word itself, such as at a morpheme boundary.
