One usually writes , where is the vertical cross section of and is the projection onto the second coordinate. On a graph, a typical entourage is drawn as a blob surrounding the "" diagonal; all the different 's form the vertical cross-sections. If , one says that "x" and "y" are "-close". Similarly, if all pairs of points in a subset of are -close (i.e., if is contained in ), "A" is called "-small". An entourage is "symmetric" if precisely when . The first axiom states that each point is -close to itself for each entourage . The third axiom guarantees that being "both -close and -close" is also a closeness relation in the uniformity. The fourth axiom states that for each entourage there is an entourage that is "not more than half as large". Finally, the last axiom states that the property "closeness" with respect to a uniform structure is symmetric in "x" and "y".