There is no single answer to this question, both 
because there appears to be considerable 
individual variation among speakers, and because 
there are very complex factors which must be taken 
into account.Ervin and Osgood (1954; following Weinreich 1953) 
suggested a three-way possibility for how 
languages relate in an individual's mind, which are 
called coordinate, compound, and subordinate 
bilingualism