Linguistic issues concerning the euro

Several linguistic issues have arisen in relation to the spelling of the words euro and cent in the many languages of the member states of the European Union, as well as in relation to grammar and the formation of plurals.

In official documents, the name "euro" must be used for the nominative singular in all languages, though different alphabets are taken into account and plural forms and declensions are accepted. In documents other than EU legal texts, including national legislation, other spellings are accepted according to the various grammatical rules of the respective language. For European Union legislation, the spelling of the words for the currency is prescribed for each language; in the English-language version of European Union legislation the forms "euro" and "cent" are used invariantly in the singular and plural, even though this departs from usual English practice for currencies.

In Asturian, there has been a controversy about the spelling of the word. The official academic dictionary uses the spelling euru, respecting the Asturian tendency to write nouns with a final -u. However, considering that the international use is euro and that there is a tendency in Asturian to write some short forms with a final -o (like euro from Europa), other linguists, like Ramón d'Andrés, defend the spelling euro.

Bulgarian uses Cyrillic. The current design of euro banknotes, except for the "new" €5, €10 and upcoming €20 banknotes, has the word euro written in Latin and Greek alphabets. The 2013 design of the € 5 banknote introduced Cyrillic, adopting the spelling ЕВРО, as described below. When Bulgaria will issue Euro coins, if the Greek model is followed, the alternative spelling will go on the national (obverse) side.

...
Wikipedia