User: What is the difference between hardwood and softwood?
Assistant: These refer to two very large categories of wood species. Softwoods are generally fast-growing trees such as pine and fir commonly found throughout the world. They are most commonly used for construction and large volume projects as they are cheaper to produce and readily available, as the trees themselves do not take as long to grow. Hardwoods, on the other hand, are called "hard" because of much denser grains: compared to softwoods, hardwoods weigh more per volume due to this property. In other words, a board of walnut (a hardwood) weighs more than a board of the same size of pine (a softwood). They are more expensive because the trees take longer to grow and are typically more rare, but are used in fine wood-crafting arts like furniture making due to their robustness and beauty in the grain structure.