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What are the major dialects of the Breton language?

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The old walled city of Saint-Malo, Brittany région, France. — Brittany The old walled city of Saint-Malo, Brittany *région*, France.

The Breton language is traditionally associated with four dialects, which are named after the four historical bishoprics of Brittany where they were spoken:1

Kerne (Cornouaille)
Leon (Léon)
Treger (Tréguier)
Gwened (Vannes)

While these four are often cited as distinct dialects, linguistically, only Gwened differs significantly from the others. This distinction arises from its unique stress accent on the final syllable and differences in vowel aperture. In contrast, the other three dialects (Kerne, Leon, and Treger) share a stress accent on the penultimate syllable, similar to Welsh and Cornish.12

Historically, the development of separate written standards in each bishopric contributed to the perception of these four distinct dialects. Efforts to standardize the language have often grouped the first three under the "KLT" norm, while the Gwened dialect has frequently required a separate norm due to its distinct characteristics.12