In today's world there are many cases, in which several languages live close to each other, even in very small areas. Bilingualism and multilingualism cases, more other less stable, in which two or more languages have been next to each other for long periods of time, without any of them being left aside, are very common. Indeed, it is very difficult to identify any country as strictly monolingual, since the multilingual communities are the great majority. Apparently, there are about 5000/6000 languages on the world, and about 200 states only. Language contact is therefore an every day and universal fact. The linguistic situation in The Basque Country, all nuances needed taken into account, it is a situation in my opinion of diglossic social bilingualism. In our community we have two languages (Basque and Spanish ), one of which has been used only in informal situations, while the other, Spanish, at least until very recently, has been considered as the culture language and the only one to be used in formal situations.

El propósito del presente trabajo trata de dar cuenta de los resultados lingüísticos de la situación de lenguas en contacto, en la que se encuentra una comunidad bilingüe, como la del País Vasco, con dos lenguas en presencia, euskera y castellano. Se examinan los procesos de interferencia del euskera sobre el castellano y los casos, en su diversa tipología, de alternancia y/o mezcla de códigos , en hablantes bilingües , con el euskera como L1.