In code switching, there is no such integration. Both languages are “on” at the same time. Code switching, therefore, presupposes a much higher degree of bilingualism than borrowing does. A speaker of Swahili can use English loanwords like soka ‘soccer; football’ without knowing any English himself, because these words have already been integrated into Swahili. To participate in code-switching between Swahili and English, however, he needs to have at least a basic knowledge of both languages.

We used to do this, and I am sure they still do, at la Iglesia de Cristo de lengua espanola de Genebra, Suisa. We’d start a sentence in Spanish and then switch to French. By the end of the sentence, or the paragraph, we would have switched back. Spanish was, of course, the primary language. But everyone there lived in French speaking Switzerland, so they also spoke French. There are some words I never learned in French because I knew them in Spanish and didn’t have to learn them.

I did not, however, learn much of Catalunan. The only expression I know in that is the translation for “dunce.” (I got called it way more often than needful.)