Estonia, officially the Republic of Estonia (Estonian: Eesti or Eesti Vabariik; Germanic languages: Estland), is a country in Northern Europe. Estonia has land borders to the south with Latvia and to the east with Russia. It is separated from Finland in the north by the Gulf of Finland and from Sweden in the west by the Baltic Sea. Estonia has been a member of the European Union since 1 May 2004 and of NATO since 29 March 2004. The Estonians are a Finnic people closely related to the Finns, with the Estonian language sharing many similarities to Finnish. The modern name of Estonia is thought to originate from the Roman historian Tacitus, who in his book Germania (ca. AD 98) described a people called the Aestii. Similarly, ancient Scandinavian sagas refer to a land called Eistland. Early Latin and other ancient versions of the country's name are Estia and Hestia.