The english function name ISNA() has been translated into 16 languages. For all other languages, the english function name is used. There are some differences between the translations in different versions of Excel.
Different translations for Excel 2010 SP1
Different translations for Excel 2010
Links to the Microsoft Online Help for the function ISNA()
Note: Microsoft is currently updating the links and contents for the Excel online help. Therefore, some of the following links may not work as expected and lead to an error page. The links will on this site will be updated as soon as possible.