Nodes (or, sometimes, "nodules") are calluses that form on the vocal cords in response to misuse. If you're lucky, they'll go away by themselves. If you're typical, you'll have to have surgery.

When I met my college girlfriend, she had just had node surgery, and was prohibited to speak. We met at the music library, where we worked as desk clerks, helping people find things and checking materials in and out. Because she couldn't speak for those first few weeks, we communicated by leaving notes for each other on the desk blotter.