The Finnish dialects are divided into two distinct groups, the Western dialects and the Eastern dialects. The dialects are entirely mutually intelligible and characterized only by minor changes in vowels, diphthongs and rhythm, and as such, they are better classified as accents. For the most part, the dialects operate on the same phonology, grammar and vocabulary. There are only marginal examples of sounds or grammatical constructions isolated to some dialect, not found in standard Finnish. Two examples are the voiced dental fricative found in Rauma dialect and the Eastern excessive case.
The classification of closely related dialects spoken outside of Finland is a politically sensitive issue that has been more or less controversial since Finland's independence in 1917. The speakers of Karelian language in Russia and of Meänkieli in Sweden are typically considered oppressed minorities. Karelian is different enough from standard Finnish to have its own orthography. Meänkieli is a northern dialect, entirely intelligible and interchangeable with any other Finnish dialect that got the status as a minority language in Sweden for historical and political reasons.
The South-West dialects (lounaismurteet) are spoken in Finland Proper and Satakunta. Their typical feature is abbreviation of word-final vowels, and in many respects, they resemble Estonian. The Tavastian dialects (hämäläismurteet) are spoken in Tavastia. They are closest to the standard language, but feature some slight vowel changes, such as the opening of diphthong-final vowels (tie -> tiä, miekka -> miakka, kuolisi -> kualis). The Southern Ostrobothnian dialects (eteläpohjalaiset murteet) are spoken in Southern Ostrobothnia. Their most notable feature is pronunciation of 'd' as a tapped or even fully trilled /r/. The Middle and North Ostrobothnia dialects (keski- ja pohjoispohjalaiset murteet) which are spoken in Central and Northern Ostrobothnia. The Far-Northern dialects (peräpohjalaiset murteet) are spoken in Lapland. These dialects spoken in the western parts of Lapland are recognizable by addition of extraneous 'h' sounds into positions where they are not found in other dialect.
One of the Far-Northern dialects, Meänkieli, which is spoken on the Swedish side of the border that was created in 1809, is taught in some Swedish schools as a distinct standardized language. The categorization of Meänkieli as a separate language is controversial among the Finns, who see no linguistic criteria, only political reasons, for treating Meänkieli differently than other dialects of Finnish.
The Ruija dialect (Ruijan murre) is spoken in Finnmark (Finnish Ruija), in Norway. It is remnant from Finnish emigrants in the 18th and 19th centuries.
The Eastern dialects consist of the widespread Savonian dialects (savolaismurteet) spoken in Savo and near-by areas. The South-Eastern dialects (kaakkoismurteet) are spoken in South Karelia, on the Karelian Isthmus and in Ingria. They retain the phonetic palatalization found in all Uralic languages except Western Finnish. Per Finnish orthography, this is denoted with a 'j', e.g. vesj, cf. standard vesi.
Usually, a distinction is made between a more distantly related Karelian language that is spoken in those parts of Karelia that never have been ruled from the West. However, the terms Karelian and Karelian dialects are often used without distinctions, primarily denoting dialects spoken on the Karelian Isthmus and n Ingria, i.e. in the Saint Petersburg area, but in a way that diplomatically may leave open for interpretation the question of whether the speaker considers the Karelian language a dialect of Finnish or not. Hence, the many refugees from Finnish Karelia, that were evacuated during World War II and resettled all over Finland, speak Savonian dialects, although their dialects in everyday speech often are referred to as Karelian.