A unit is a single structure of a certain ring connectivity, forming a unique connection pattern which, when finished, is complete and would no longer have any rings added to it.
A chain is a weave form which is expandable on only one plane in both of two opposing directions.
A sheet is a weave form which is expandable on either of two planes, each in both of two opposing directions opposite each other when laid out flat. This weave form creates a mesh which can be expanded to fill a certain area.
The dimensional weave form refers to weaves that can be expanded on either of three different planes. This weave form creates structures that can be expanded to fill a certain volume.