In the poem "The Last Leaf" by O. Henry, the poet says "No" in the beginning of the third stanza to reject the idea of Johnsy giving up on life.
This is a significant moment because Johnsy, who is very ill with pneumonia, has become convinced that she will die when the last leaf falls from the vine outside her window. The poet is expressing his disagreement with Johnsy's negative mindset, emphasizing that life should not be surrendered so easily.
By saying "No," the poet is refusing to accept the idea that a person’s life is dependent on something as trivial as a falling leaf. He underscores the importance of hope, strength, and the will to live in overcoming even the hardest of situations.
This "No" symbolizes a call to action, urging Johnsy to fight against her despair and believe in her recovery despite the circumstances. It reflects the central theme that hope and willpower are just as important as medical treatment when it comes to overcoming illness.