What does 衰退 mean?
衰退 is a Japanese noun meaning “decline; degeneration; decay; waning” in English. It is written as 衰退 in kanji, すいたい in hiragana, and suitai in romaji. This word is part of JLPT N1 vocabulary.
Example sentence
４７５年はローマ帝国の「衰退」を示す年ではあっても、「滅亡」を意味する年ではありません。
Although 475AD is the year that shows the 'decline' of the Roman Empire, it is not the year of its 'fall'.