What do you know about textile fibers?

Elasticity

There are actually two parts to elasticity. The first is stretch or elongation. This measures how far we can pull and lengthen a fiber. The second part is recovery. This is how close can the fiber return to its original length after stretching.
Stretch is key for comfort, especially in form-fitting clothes. It is what allows us to move freely. It also helps to add to the longevity of a garment by reducing the tension placed on seams, helping them to not split and last longer. And, as an added bonus it also increases the strength of fabrics.
There is a special category of elastic textile fibers, they are elastomeric fibers. Spandex and rubber belong to this group. Elastomeric is basically just a fancy word that means a fiber can stretch over 100% its original length.

Hand

Hand describes how a fabric feels. It is highly subjective. Is it smooth, scratchy, stiff, cool, crisp, dry, warm, fuzzy, etc?

Hydrophilic

Hydrophilic means that a fiber loves water and can absorb a lot of it. And, an example of a hydrophilic fiber is cotton.

Hydrophobic

Hydrophobic means that a fiber does not like water. These textile fibers also tend to oleophilic. This means that they like oil, and will absorb oil. An example of a hydrophobic fiber is polyester.

Luster

Luster describes how light reflects from the surface of a fiber. Fibers with high luster are very shiny. High luster fibers tend to be very smooth and round like many synthetics. Fibers like wool, that have crimp or are scaly or irregular shapes, will have lower luster and appear dull. The types of twist in yarns and the type of weaves and knits can also effect luster.

Pilling

Pills are the little balls of fuzz that build up on your clothing. Pilling happens because of tiny broken fibers.
Hydrophobic fibers (textile fibers that repel water) tend to pill more than hydrophilic (textile fibers that like water) fibers. This is because hydrophobic fibers they have more static build-up, and end up clinging together on the surface of the fabric instead of falling off.
Wool is an exception to the rule. Wool, although hydrophilic, tends to pill because the surface of the wool fibers is scaly and the scales stick to each other and to the fabric.