Aspen, for one, is a term that can refer to a tree, a POPLAR, or a ski resort. The tree is a four-letter word, the POPLAR is a six-letter word, and the ski resort is a nine-letter word. Aspen is a type of tree that is native to cold climates in the Northern Hemisphere, and is known for its white bark and leaves that turn yellow in the fall. Poplars are a type of tree that are related to aspens, and are also found in cold climates. Aspen is also a popular ski resort town in Colorado, USA, which is known for its beautiful mountain scenery and excellent skiing conditions.