Absorption and transpiration are two different processes, though. Cotton IS very good at absorbing water, which is why it sucks so much to wear it. When something Absorbs a fluid, it takes it into itself. Cotton wicks water into its structure - - like, into the actual individual strands of thread, where air and wind can't get to it, to evaporate it.

If you take something like wool, on the other hand, the hairs themselves do not actually absorb water in the same way that cotton does. This is wonderful, because they simply pull the water ALONG the hairs via surface tension and capillary forces, rather than pulling the water INTO itself. This exposes the water to air on the other side of the fabric, allowing it to evaporate.

The same is true of polyester, which is why poly is the go-to cheap sports fabric, and wool is the king of sports and sweating fabric when you don't need the structural properties of poly.

Try it for yourself. Wear a pair of merino wool socks for a few weeks, then go back to cotton. It feels like you're standing in a puddle by comparison. The cotton simply traps moisture against your skin.