Autonomy and heteronomy are complementary attributes of a language variety describing its functional relationship with related varieties. The concepts were introduced by William A. Stewart in 1968, and provide a way of distinguishing a language from a dialect. Definitions A variety is said to be autonomous if it has an independent cultural status. This may occur if the variety is structurally different from all others, a situation Heinz Kloss called abstand. Thus language isolates such as Basque are necessarily autonomous. Where several closely related varieties are found together, a standard language is autonomous because it has its own orthography, dictionaries, grammar books and literature. In the terminology of Heinz Kloss, these are the attributes of ausbau, or the elaboration of a language to serve as a literary standard. A variety is said to be heteronomous with respect to a genetically related standardized variety if speakers read and write the other variety, which they consider the standard form of their speech, and any standardizing changes in their speech are toward that standard. In such cases, the heteronomous variety is said to be dependent on, or oriented toward, the autonomous one. In the terminology of Heinz Kloss, the heteronomous varieties are said to be under the "roof" of the standard variety. For example, the various regional varieties of German (so called "dialects"), such as Alemannic, Austro-Bavarian, Central, Eastern, and Northern Hessian, Kölsch, Low German, and more, are heteronomous with respect to Standard German, even though many of them are not mutually intelligible. A dialect continuum may be partitioned by these dependency relationships, which are often determined by extra-linguistic factors. For example, although Germanic varieties spoken on either side of the Dutch–German border are very similar, those spoken in the Netherlands are oriented toward Standard Dutch, whereas those spoken in Germany are oriented toward Standard German. Within this framework, a language may be defined as an autonomous variety together with all the varieties that are heteronomous with respect to it. Stewart noted that an essentially equivalent definition had been stated by Charles A. Ferguson and John J. Gumperz in 1960. In these terms, Danish and Norwegian, though mutually intelligible to a large degree, are considered separate languages. Conversely, although the varieties of Chinese are mutually unintelligible and have significant differences in phonology, syntax and vocabulary, they may be viewed as comprising a single language because they are all heteronomous with respect to Standard