Why do people hold that United States is more properly called a republic rather than a democracy?

Some people insist that the us is more properly called a republic rather than a democracy. They hold taht in a republic the sovereign power is held by those eligible to voe, while the political power is exercised by representatives chosen by and held responsible to those citizens. For the, democracy can be defined only in terms of direct democracy. Whatever the terms used, remember that in a democracy the people are sovereign. They are the only source for any and all of government's power. in other Words, the people rule.