Sei is a term that can refer to various concepts depending on the context. In Japanese culture, it often relates to the idea of purity or cleanliness, which is significant in practices like Shinto and Zen Buddhism. The concept emphasizes harmony with nature and the importance of maintaining a clear mind and environment. In the context of literature, Sei Shonagon was a notable Japanese author and court lady during the Heian period. She is best known for her work, The Pillow Book, which is a collection of essays, lists, and anecdotes that provide insight into court life and the aesthetics of her time.