The toponyms of Finland result mainly from the legacy left by three linguistic heritages: the Finnish language (spoken as first language by about 93% of the population), the Swedish language (about 5.5%) and Sami languages (about 0.03%). Finland’s place names range from those of unknown or unrecognizable origins to more clearly derivable onomastics. There are both national and international recommendations on how to use the bilingual country's place names in texts written in different languages. In Finland, the Research Institute for the Languages of Finland and the National Land Survey of Finland are jointly responsible for the standardization of place names.
A few notable place names – such as a few major hydronyms Päijänne, Saimaa, Imatra and Keitele which are thought to be among the oldest toponyms – still lack a sound derivation from existing languages despite of different approaches. This has led to the postulation that they may originate from an unknown language. A substratum of archaic Sami place names, often fennicized in the course of time, can be found throughout the country. The majority of Finland’s toponyms can be recognized having archaic or dialectal Finnish origins. A Finnish substratum can be deduced in Swedish place names and vice versa in many cases. Major urbanisation started and city rights were granted in Finland when the country was part of Sweden in a situation where Swedish was the de facto only official language though the majority always spoke Finnish dialects as a first language. Therefore, in older foreign writing, many municipal and city names are given only in their Swedish form. Other substrata in Finland’s toponyms include Finnic, Baltic, Germanic and Slavic linguistic influence in several chronological layers.
Finland, except for the Åland islands, has two official languages: Finnish and Swedish. The Åland islands have a single official language: Swedish. On the mainland, Swedish-speakers are concentrated to the regions Ostrobothnia, Uusimaa and around Turku. North Sami, Inari Sami and Skolt Sami are semi-official in the Sami Domicile Area. The Language Act of 2003 groups municipalities into three groups: monolingually Finnish, monolingually Swedish and bilingual. The municipality is monolingual, if it has less than 8% of the minority language speakers and if the population of the lingual minority in the municipality is below 3,000. Other communities are bilingual.