Texture describes the three dimensional character of a surface. It can vary from perfectly smooth to very rough and be regular or random. Rough and smooth textured surfaces reflect light differently. A very rough texture will appear different when illuminated from different angles (image 1.)
As part of a fabric, yarn texture contributes another layer of design complexity. The irregular texture of a yarn can be the primary design element of a simple fabric, or a smooth yarn highlights a complex structure by not providing a distraction. If the yarn has thick and thin sections, the resulting fabric will also have thick and thin areas. Textured yarns are frequently used with simple weaving and knitting patterns but less with complex crochet or lace. Highly textured yarns make difficult warps because they can stick together, abrade in the heddles or reed or break easily.
Maximum 12 points
I'm not sure why I got full points on this item and not the others, because they are all written with the same general discussion of how yarn design affects fabric design. Short of a detailed treatise on the four specified fabric construction methods, I don't know how to address this. I thought this was supposed to be more about the yarn, and a general discussion of fabric design seemed an obvious interpretation of the question. This item does mention all four of the construction techniques by name, but some are also given in specific examples in the others. And there are other ways of making fabrics than just weaving, knitting, crochet and the various types of lace.
I disagree with the expectation that textile design should fit in the neat boxes of European Formalism, so it was extremely difficult for me to write all of these Principles of Design items. Art criticism only considers visual design and has standards that are by no means universal. This entire section was by far the one I hated most because I saw it as eurocentric, stuffy art-for-art's-sake. I enjoy textiles because they are tangible objects with a practical purpose, in addition to something that can also show complex visual design. I get very frustrated with displays of textiles hung on walls with little cards that say nothing about the structure or anything having to do with the fact that it is a functional textile other than maybe the fiber content. I don't give my fabrics titles, either.