Timely Topic, Confusing Terminology

Discussion of “Why We Need Civics” is certainly timely.  But the terminology used in the article is confusing as to what form of government the author thinks we have.  First, Professor George is quoted as stating that the U.S. is not a democracy, but a republic.  Then, one Emma Humphries is quoted as calling the form of government “our constitutional democracy” — apparently with the approval of the author, as he later adopts that term without quotation marks. It does not appear to me that the term “constitutional democracy” means “republic,” but rather implies that some constitutional provision requires that the form of government be a democracy. If so, where is that provision? So which do we have —republic or democracy? The  article is confusing in using both terms as if they were synonyms, but very helpful in discussion of its important topic.