How modify the translation of a bibtex field?

Question

When I use the "translator" field in bibtex (with fontspec and Italian as mainlanguage), for example in a entry like the following one:

    @Book{ apollodoro:2013,
    author                   = "Apollodoro",
    title                    = "Biblioteca",
    editor                   = "P. Scarpi",
    translator               = "M. G. Ciani",
    publisher                = "Valla Mondadori",
    location                 = "Milano",
    year                     = "2013\textsuperscript{2}",
    }

I obtain "trad. da. M. G. Ciani". For, in my opinion, the most common and correct way to translate that string is "trad. it. di M. G. Ciani", I ask you if there is a way to change the current Italian tranlation.

Answer 1

The string in question here corresponds to bytranslator, whose Italian localization can be found in the file italian.lbx; you can change the default definition using \DefineBibliographyStrings:

\documentclass{article}
\usepackage{fontspec}
\usepackage{polyglossia}
\setmainlanguage{italian}
\usepackage{biblatex}

\makeatletter
\DefineBibliographyStrings{italian}{%
  bytranslator     = {{trad\adddot\ it\adddot\ \lbx@sfromlang\ di}}
}
\makeatother

% this section is just for the example
\usepackage{filecontents}
\begin{filecontents*}{test.bib}
@book{apollodoro:2013,
    author                   = "Apollodoro",
    title                    = "Biblioteca",
    editor                   = "P. Scarpi",
    translator               = "M. G. Ciani",
    publisher                = "Valla Mondadori",
    location                 = "Milano",
    year                     = "2013\textsuperscript{2}",
    }
\end{filecontents*}
% end of section for the example

\addbibresource{test.bib}

\begin{document}

\cite{apollodoro:2013}
\printbibliography

\end{document}