Just as people are aware of the electronics brand named “Apple”, so are most people familiar with the material called Lycra (spandex). Lycra was invented by Dupont as a stretchable synthetic fiber, made by a more complex technique than nylon. The most common brand neutral references to the material is spandex or elastane. While similar to nylon, it is much more stretchable. However, it is not as durable as nylon. A garment made completely of spandex would be prone to tears and have difficulty keeping form. This is why spandex is frequently blended with nylon, so that you get the benefits of both materials. I should point out that spandex is made in four different ways, and each method may result in some characteristic differences.
The percentage of spandex versus nylon results in different benefits and drawbacks that are important to be aware of when buying hosiery.