1. Materials: The quality of the materials used in the construction of furniture can have a significant impact on its durability, comfort, and appearance. High-quality materials such as solid wood, leather, and high-density foam tend to be more desirable than cheaper materials that may wear out quickly or look cheap.
2. Design: The design of furniture can play a big role in its quality. A well-designed piece of furniture should be functional, aesthetically pleasing, and durable. It should also be comfortable and easy to use, with features that make it easy to clean and maintain.
3. Craftsmanship: The level of craftsmanship that goes into the construction of furniture can also have a big impact on its quality. A well-made piece of furniture will have smooth edges, tight joints, and consistent finishes, while a poorly made piece may have rough edges, loose joints, or other signs of poor workmanship.
4. Comfort: Comfort is an important factor to consider when evaluating the quality of furniture. A comfortable piece of furniture should provide adequate support, be easy to adjust, and feel good to sit or lie on.
5. Durability: The durability of furniture is another important factor to consider. A high-quality piece of furniture should be able to withstand everyday wear and tear, and should last for many years without showing signs of significant wear or damage.

Overall, the quality of furniture can be defined in a combination of materials, design, craftsmanship, comfort, and durability. A high-quality piece of furniture should be well-made, aesthetically pleasing, comfortable, and durable, and should be able to withstand everyday use without showing signs of wear or damage.