An ELT Glossary : Code switching

Code switching is a common feature in the speech of bilinguals. When talking to each other they may change from one language to another even within the same sentence. For example, the other day I said to my son : 

My phone's scarico, dunque if you need me, use the office number.
scarico, dunque = Italian for dead (in the sense of needing recharging) so

Codeswitching is often "triggered" by the obligatory use of a word from the foreign language, such as a name. Using the word "converts" the speaker's brain to thinking in the other language. Talking about going to our local supermarket I also once said I'm going to Esselunga - abbiamo bisogno di latte  (= I'm going to Esselunga - we need some milk.)