Dui (marsh) is one of the eight trigrams, bundled together in the shape of ☱. It is also one of the 64 hexagrams, composed of two trigrams like this ䷹. In the eight-trigram system, it symbolizes the marsh or lake. The marsh fosters all forms of life, therefore making everything pleasant. The term is composed of one broken line and two unbroken lines. It is considered a yin trigram and a symbol for the female. Since the broken line lies above the two whole lines, it is considered to stand for the youngest daughter of a family.
Dui denotes pleasure. (The Book of Changes)
Dui stands for two connected bodies of water, and represents pleasure. Thus does a scholar engage with like-minded friends in learned disciplines. (The Book of Changes)