There are a number of reasons for O. Henry's lengthy description of Della's hair.
- He wants to show how proud she is of her hair and how important it is to her. This will make her sacrifice of it seem all the greater. There has to be a description of Della with her hair for the strong contrast with Della without her hair.
- The description of Della with her long and beautiful hair will make the contrast greater when she is shorn of it and has to try her best to cover her head with tiny curls which make her look like "a truant schoolboy" or "a Coney Island chorus girl."
- The fact that her hair is so valuable to her gives her the idea of selling it. It is the one way she can raise a substantial amount of money. Madame Sofronie is undoubtedly glad to get such a large quantity of beautiful, youthful hair.
- The reader is made to feel Della's pain when she goes to Madame Sofronie and has to have all her hair cut off.
- Della's beautiful hair is what gives Jim the idea of buying her the set of tortoise-shell combs for a Christmas present. Jim knows she covets them.
- There is a real possibility that Jim will cease to love Della because the loss of her hair means the loss of much of her beauty.
- This is not a story of two young people making sacrifices for each other. Jim only plays a minor role at the end and is seen only through Della's point of view. It is Della's story. We are in her point of view from beginning to end. People will always remember "The Gift of the Magi" as a story about a young woman who sold her hair to buy her husband a Christmas present. Della's hair is the most important thing in the whole story.
O. Henry describes Della's clothing only to show how poor she is.
On went her old brown jacket; on went her old brown hat.
The author describes many features of the Youngs' apartment for the same purpose. They include the faded business card by the bell downstairs, the pier glass, the shabby little couch, and the worn red carpet.