Sauna terms divide Finland along a century-old linguistic line

A linguistic divide between the words vihta and vasta—both meaning a bundle of birch twigs used in saunas—has persisted in Finland for nearly a century, according to a new survey by Yle and the University of Eastern Finland.

Over 38,000 Finns responded to the survey, revealing a clear geographical split: vihta dominates in western Finland, while vasta is predominantly used in the east. Both terms are accepted in standard Finnish.

Professor Hanna Lappalainen of the University of Eastern Finland called the stability of the divide “astonishing.” A 1932 map by linguist Kustaa Vilkuna shows the boundary between the two words in nearly the same location as today.

“These two maps are strikingly similar,” Lappalainen said. She suggested the persistence of both terms in standard Finnish has helped maintain the divide.

The survey also collected over 7,500 written comments, many revealing strong personal connections to the words, with some respondents noting mixed usage due to family origins from different regions.

Lappalainen noted that the boundary between vihta and vasta closely follows the 1323 Treaty of Pähkinäsaari border, a historical division that has influenced other linguistic, genetic, and cultural patterns in Finland.

The data will be used for future research by the University of Eastern Finland’s Finnish language department. Yle and the university have previously collaborated on studies of pronoun usage, terms for “mother,” greetings, and the occurrence of the d sound in Finnish speech.