width
returns the minimum diameter of the geometry, defined as the smallest band that contains the geometry, where a band is a strip of the plane defined by two parallel lines. This can be thought of as the smallest hole that the geometry can be moved through, with a single rotation.
clearance
returns the minimum clearance of a geometry. The minimum clearance is the smallest amount by which a vertex could be moved to produce an invalid polygon, a non-simple linestring, or a multipoint with repeated points. If a geometry has a minimum clearance of 'mc', it can be said that:
No two distinct vertices in the geometry are separated by less than 'mc'
No vertex is closer than 'mc' to a line segment of which it is not an endpoint.
If the minimum clearance cannot be defined for a geometry (such as with a single point, or a multipoint whose points are identical, NA is returned.