# Definition of Grid types and terms:

These are terms used in the pages created under CdlDiscussion Please change them as needed but be sure to change them everywhere so we know what we are talking about.

**Grid**

The name for an unstructured grid on which data is located

**Cells**

The geometric components of a grid

**Nodes**

The vertices of the geometric cells of a grid

**Edges**

The lines which connect the vertices of a geometric cell

**Faces**

The 2D polygons which bound a 3D geometric solid cell

**Connectivity**

A list of the Nodes which describe the geometric shape of an cell in a pre-formatted order

A mesh which is uniform in one of its dimensions. --

think cookie cuter?

*Edge List*

A list of the edges which bound a cell in a pre-formatted order

*Cell_Adjacency*

A list of the faces which bound a cell in a pre-formatted order

*Node_Neighbors*

A list of the indices of the nodes which are connected to the central node. This array of indices would seem to be a "ragged" array, as a central node may be connected to two to many (but probably less than 10 in 2D) nodes.

These definations do not stand by themselves. The dimensions of these data objects go a long way to describ them. This is in some sense the meaning of "coordinate" variables. The coordinate dimensions make a real connection between the different data objects. All objects with a dimension of "nodes" are understood to be values which are valid at the nodal points. Which nodal points make up a cell is a different matter. But knowing that the cell is using the nodes coordinate for its corners tells you what variables are defined on the corners of the cells.

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