The phrase "Diet of Japan" refers to the legislative body of the country, which is comprised of the Upper and Lower Houses. Synonyms for this phrase include "Japanese parliament," "National Assembly of Japan," and "Japanese Congress." The term "Diet" itself is a translation of the Japanese word "Kokkai," which means "national assembly" or "national diet." The Diet of Japan is responsible for making and modifying laws, approving the national budget and treaties, and electing the Prime Minister. This powerful governing body helps to shape the political landscape of Japan and plays a crucial role in the country's political and social evolution.