Code-switching in writing can be defined as the switch from one language to another within a single text, comparable to the definition of spoken code-switching as the use of more than one language within the same conversation or sentence. Code-switching is characterized by its use by bilinguals and its relative spontaneity (or, perhaps better for the written medium, its flexibility and lack of fixedness), whereas borrowing designates forms incorporated into the receiving language and also used by monolinguals. This might sound straightforward,but identifying switches can be problematic. Borrowing and code-switching reside on a continuum and the linguistic classification is not attached to the words absolutely, but may depend on time period, linguistic groups, context, and the preferences of the individual. Modern sociolinguists struggle with a range of problems in diagnosing and analysing contemporary code-switching, but these problems are multiplied when we tackle ancient written material.
Despite the problems with identification, categorization and interpretation, code-switching offers a unique opportunity to approach afresh some major socio-cultural issues. With the new online database of code-switching in Roman literature and a range of approaches, historical, literary and (socio)linguistic, to be explored and combined, the possibilities for future research seem endless. Detailed empirical investigations into the form and function of code-switching across different genres, authors and contexts allow us, for example:
For code-switching in the ancient world, see Adams 2003, Adams, Janse and Swain 2002, Elder and Mullen 2019, Jocelyn 1999, Mullen 2015, Mullen 2013 (especially chapter 3), Mullen and James 2012, Rochette 2007, Swain 2004, Wenskus 1998.
For introductions to the vast corpus on code-switching in the modern world, see Gardner-Chloros 2009, Milroy and Muysken 1995, Myers-Scotton 2006. See Gardner-Chloros and Weston 2015 for a volume which treats code-switching in literature, ancient and modern.