code

sociolinguistics perspective                                                  

When two or more people communicate with each other in speech, we can call
the system of communication that they employ a code. In most cases that code
will be something we may also want to call a language. We should also note that
two speakers who are bilingual, that is, who have access to two codes, and who
for one reason or another shift back and forth between the two languages as
they converse by code-switching  are actually using a third code,
one which draws on those two languages. The system (or the grammar, to use a
well-known technical term) is something that each speaker ‘knows,’ but two very
important issues for linguists are just what that knowledge is knowledge of and
how it may best be characterized.