This appendix will provide a very basic introduction to networks. This introduction is by no means comprehensive, but should be sufficient for those without network analysis experience to begin following the workflows in section 5 Sample Workflows. Networks, sometimes referred to as graphs, are comprised of two basic elements: points and lines. The points in a network represent entities and lines represent the relationship(s) that connect these points. The simple example below will illustrate this point:

These points and lines are often referred to by different terms. The table below should help you decipher any terms you encounter.

Points | Lines |
---|---|

Vertices | Edges, Arcs^{*} |

Nodes | Links |

Throughout this manual we will refer to points as nodes and the lines as edges or arcs.^{*}Arcs are directed edges, meaning that the relationship has a direction. You will see an example later in this introduction in the edge attribute section.

## Node Attributes

Some important node attributes include:

**Betweeness Centraility** - is the number of shortest paths a node sits between. In the case of the network below, **Node ****A** has the highest betweeness centraility because it sits between four edges that connect to other nodes.

**Degree** - is the number of edges that connect to a node. For example,** Node A** has a degree of four and **Node F** only has a degree of 2.

**Isolates** - are nodes that are not connected to any others through edges. In the network below **Node G** is an example of an isolate.

## Edge Attributes

Some important edge attributes include:

**Shortest paths** - shortest distance between two nodes. For example the shortest path from **Lenore **to **Mary** is through **Rupert** and not through **Chris **and **Jessica**.

**Weight** - strength of the tie represented by the thickness of the edges between nodes. In the example below, the edge between **Lenore** and **Chris **is the strongest.

**Directionality** - is the connection one-way or two-way? In the example below, and in most directed networks, directionality is indicated by arrows.

**In-degree** - is calculated by determining the number of edges that point to a node, for example **Chris **has an in-degree of 3 and **Rupert** only has an in-degree of 1

**Out-degree** - is calculated by determining the number of edges that point away from a node, for example **Chris **has an out-degree of 1 and **Rupert** has an out-degree of 3.