Katharevusa is a highly formal and purist form of the Greek language, which is characterized by the use of complex grammatical structures and archaic vocabulary. Some common synonyms for Katharevusa include "puristic Greek" or "high Greek," which are used to describe the use of this formal language in literary and academic settings. Additionally, "classical Greek" or "ancient Greek" are used to describe the ancient Greek language, which served as the basis for Katharevusa. On the other hand, "demotic Greek" or "common Greek" refers to the modern and colloquial form of the language used in everyday conversation.