It's not a claim at all. It's a definition of a word. If we don't agree on what a word means, we can't communicate.
If, say, a peacekeeping force is instituted and its goal is *not* to keep the peace, but something else, it's not really a peacekeeping force, it's a sham of a peacekeeping force, because an actual peacekeeping force's goal is to keep the peace, by definition. Similarly, if a democracy is falling far short of expressing the will of the people, it's not really a democracy, by definition.