Diglossic languages (and diglossic language situations) are usually described as consisting of two (or more) varieties that coexist in a speech community; the domains of linguistic behavior are parceled out in a kind of complementary distribution. These domains are usually ranked in a kind of hierarchy, from highly valued (H) to less valued (L); when the two varieties are recognized (or tacitly accepted) as genetically related, the H domains are usually the reserve of the more conservative form of the language, which is usually the literary dialect if there is a written form. `Formal' domains such as public speaking, religious texts and practice, education, and other prestigious kinds of usage are dominated by the H norm; the L norm is used for informal conversation, jokes, street and market, the telephone, and any other domains (e.g. letter writing, cinema, television) not reserved for the H norm. For diglossic situations involving two different (genetically unrelated) linguistic codes, (sometimes referred to as `extended' diglossia) the one dominating the H domains has the greater international prestige or is the language of the local power elite or the dominant religious community and/or its priesthood. In such cases the H-variety language is clearly the language of the more powerful section of the society, however power is defined.
Thus in French Canada, English occupies the H-variety niche because it has the greatest prestige in North America (and perhaps internationally as well), its population even within Canada is numerically greater than the community of French speakers, and its speech community is economically dominant, both in English Canada and in French Canada. Conversely, in France, French is the H-variety in diglossic situations involving other languages or dialects, such as Breton or Alsatian, where these varieties are only used as L-variety spoken vehicles in the home, on the street, in the construction trades, etc.
It remains to be seen whether the same kind of imbalance of power exhibited in non-genetic diglossia can be said to exist with regard to classical or genetic diglossia. In many diglossic situations, only a minority or elite control the H domain successfully, so those who know only L are at a disadvantage.