MyLingo

The language in which I prefer to interact online, chosen from those available at the time. This can be changed at any time, and need not be recorded.

Things not defined in this language could be free text entered by another party, in which case it is given as entered — an option to translate may later be supplied, or just left to the user. If it is not free text, but rather part of the system that has not been translated, it is given in the defined default language (usually English).