Simplify the following text for a Grade 18 native English-speaking person.
Original: The Empire of Japan ( ( ( KyÅ `` jitai KyÅ `` jitai ) ) : ; Shinjitai : ; Romaji : Dai Nippon Teikoku ; officially Greater Japanese Empire , Great Japan or Empire of Great Japan ; more widely known as Imperial Japan or the Japanese Empire ) was a Japanese political entity that existed since the Meiji Restoration on 3 January 1868 until the enforcement of the Constitution of the State of Japan on 3 May 1947 .
Simplified: The Empire of Japan ( Japanese : å æ -- æ å å 1\/2 ; said Dai Nippon Teikoku ; officially Empire of Greater Japan or Greater Japanese Empire ; also called Imperial Japan and the Japanese Empire ) was a government of the areas ruled by Japan during the period from the Meiji Restoration to the Japanese defeat in World War II .