The denser the carpet, the more durable it will be. Select a density level suitable for the traffic level where the carpet will be used. Yarns may be made of filament or staple fibers. Filaments are long fiber strands measured in miles. They often are referred to as continuous filament fibers.
Silk is the only natural filament fiber.
A mono-filament yarn is made of a single fiber filament. A multi-filament yarn is made of multiple fiber filaments. These may or may not be twisted together. When twisted and heat-set, they usually are more durable for floor coverings. Staple fibers are short fibers measured in inches or fractions thereof.