In the Introduction we discussed sehemes for classifying tectonic and metamorphic fabrics using features observable at a variety of scales. We have emphasized that descriptors used to describe such observables carry no genetic implications. Furthermore the descriptors should not overlap in meaning with other descriptors. In understanding the geometric similarities or relationships between different types of cleavage and schistosity it was necessary to resort to three-dimensional diagrams (Fig. 1.5, p4). However, the relationships are often gradational in more than three directions and in an ideal universe we would like several more dimensions in which to depict the possible transitions from one type of cleavage to another.