This article presents a general overview of the adult bilingual individual. First, the bilingual is defined and discussed in terms of the complementary principle, i.e. the fact that bilinguals acquire and use their languages for different purposes, in different domains of life, with different people. Next, the various language modes bilinguals find themselves in during their everyday interactions are examined. These range from the monolingual mode when they are communicating with monolinguals (and they have to deactivate all but one language) to the bilingual mode when they are interacting with other bilinguals who share their two (or more) languages and with whom they can mix languages if they so wish (i.e. code-switch and borrow). The article ends with a rapid survey of the psycholinguistics of bilingualism and, in particular, of how bilinguals access their lexicon when perceiving mixed speech. The regular bilingual is compared to the interpreter bilingual whenever possible.