Ak??an is a question, story, dialogue, or statement often supplemented with commentaries, that is used in Zen practice to provoke the initial insight of Zen students. Prolonged koan study shatters small-minded identification, and pride that comes with initial insight, and promotes further development of empathy, compassion, insight, and “Beginner’s Mind.”
The most famous compilations of k??ans are the Blue Cliff Record, the Book of Equanimity, The Gateless Gate, and the Collection of Stone and Sand. One of my teachers used to update some of these k??ans for 20th-century consumption.