AN AXIS IS AN IMAGINARY LINE – it is not a thing but an idea. People use this imaginary line to make sense of objects and the relationship between objects, ourselves and our environment. One definition for an axis comes from physics – it is a line that projects from the centre around which an object rotates. However, architecture does not generally include real motion or rotation, so a more useful definition of axis comes from geometry. That definition presents an axis as generated by how we perceive objects. One way we understand objects is through imagining a line that either extends from, or passes through, the centre of mass for each of the major spatial dimensions of the object. That line, as a projected extension of the object, allows us to associate that object with other objects and ideas. The idea that an axis creates an association or organizes relationships means that it cannot simply be considered as a value-free line. While the major spatial dimensions are the basic cartesian coordinates of X (length), Y (width) and Z (height), an architectural designer will make decisions about which of these are more important depending on context. This means that when we have more than one axis present in an environment, there will often be different levels of importance between them (see Hierarchy ). In this way, an axis might be considered either primary, secondary and tertiary in relation to other axes and the overall context.