You can name items and write notes in any human language.
Sometimes, however, the computer or the browser that you are using cannot display some of the characters on the page. In that case, the page may appear to be broken, but it is not. It will display just fine on another computer that supports the font used on the page. You may still add new items to the page. Note, however, that if you edit an item while it appears in funny characters, it may become "funny" forever.
If you encounter such problem, try to upgrade the browser, or add fonts to your system.
See also: