Does a dog have Buddha-nature? Wu.
Zhaozhou was in his seventies when a monk asked him whether a dog possessed Buddha-nature, the fundamental capacity for awakening that Mahayana Buddhism taught was universal. He had spent decades traveling, studying, and teaching, and by this point in his life he had stripped away nearly every unnecessary thing. His single syllable — Wu, meaning "no" or "nothing" — became one of the most studied responses in Zen history, not because it answered the question but because it refused to add anything extra to it. In a time when we habitually over-explain, qualify, and perform our understanding, that one bare word is a direct challenge.
Reflection
Think about a conversation you had recently where you kept talking past the actual point. What one word or sentence would have said everything you needed to say?