In the words of
Georges Lacombe, because of the special features of this
dialect,
Euskera could well be divided into two groups of dialects: Biscayan and the rest. He argued that this dialect was so different from the rest, that the
isoglosses separating it from the adjacent dialects (Gipuzkoan or central) are so close to each other that form a clear line; that is, the
phonetic-
phonological,
morphosyntactic and
lexical features of Biscayan coincide geographically to the point of creating a distinctively clear and defined dialectical border. Because of these differences both with the rest of the Basque dialects and also with
Standard Basque or Batua, and respecting their corresponding uses, the
Euskaltzaindia has produced a Model for Written Biscayan (), a set of rules mainly focused on
morphosyntax. The official use of the dialects of Euskera is regulated through Regulation 137 of the Euskaltzaindia, according to which the use of Batua should be limited to the fields of communication, administration and teaching. Since 1997 and according to the new dialectical classification realized by
Koldo Zuazo, author of
Euskalkiak. Herriaren lekukoak (Elkar, 2004), the name given to Biscayan is the
Western Dialect, due to its use not being limited to the province of Biscay, but with users in some
Gipuzkoan regions such as
Debagoiena (mainly) and
Debabarrena, and also some
Alavan municipalities such as
Aramaio (Aramayona) and
Legutio (Villarreal). According to a study by
Yrizar, this dialect was spoken in the seventies by around 200,000 people, with the number of estimated speakers approaching 300,000 by the eighties. In 1991 16% of the population of this province could speak Basque, and data gathered in 2001 data 22% of the total 1,122,710 Biscayans (i.e. 247,000) could speak and write in Basque. However, this data is only illustrative, as there is no record of how many of the Basque speakers spoke Biscayan specifically and it does not take into account Biscayan speakers in Gipuzkoan territory (
Bergara,
Leintz Gatzaga,
Mondragon,
Oñati, etc.) ==Subdialects and variations==