procedure textdomain(Domain:string);

This procedure changes the current textdomain, i.e. the text domain that is used by gettext(), _() and ngettext(). The default text domain, if textdomain() is not called, is 'default'.

Usually, libraries, modules and other pieces of software that are not developed together with the application that they are included in, should use another text domain. For instance, if the programmer of program A uses module B, then module B should use another text domain that 'default'.