For Paternayan, that means that you will end up with three pieces of yarn. For cottons and silks you can have more. The plys will then tend to lie parallel and therefore give you better coverage.
Synthetic yarn is great but it can be damaged by using high dryer heat.
Better yet, dry flat. When you wash wool, think of your hair. You'll be surprised at how much better the wool feels. If your yarn comes in a skein instead of a ball, take care when winding it into a ball. If you wind the ball too tightly then you will stretch out the wool and when knit, will change the gauge of your knitting.