Answer:
The last leaf shows the courage, the strength, and resilience needed to achieve success amidst the many strong obstacles that may come up. It also signifies the sacrifice of Behrman in making sure that his young neighbor has a ray of hope for her life even at the point of losing his own. And with the leaf's presence, Johnsy got more motivation and hope for her own improvement, healing her mentally and physically.
Explanation:
O Henry's short story The Last Leaf is a story about three specific characters- Sue and Johnsy who live together alongside Mr. Behrman who is also an artist. And it is with the last artistic achievement of Mr. Behrman that saved Johnsy from her dying condition, which unfortunately also led to the death of the painter himself.
Johnsy was sick with pneumonia, and she kept on counting at the ivy leaves from her bed, deciding that she will die once the last leaf fell. Day by day, when the leaves fall, she would also get herself ready to let go. Despite the doctor and her friend Sue's attempt to make her feel better, she seems to have only thoughts of death. Mr. Behrman, on learning that Johnsy kept her life hanging on the ivy leaves, decided to paint a leaf under the cold, catching pneumonia himself. The illness killed him but it also gave life to Johnsy, who saw that the last leaf isn't falling. She did not know that it was a painted image and felt that the last leaf's resilience in hanging on to the vine signifies she should also hang on to life. And in the end, the last leaf became the masterpiece of Mr. Behrman, his one and only finished art.
The last leaf signifies hope, and persistence despite the odds stacked against us. It taught us about the sacrifice that needed to be made for any success. It also signifies the encouragement that Johnsy needed to get well.