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# Graph theory

- Graph theory is the study of graphs
- a
**graph** is a mathematical data structure used to model 1-to-1 relationships between components of the graph
- graphs are made up of
**vertices** and **edges**:
**vertices**:
- AKA "nodes" or "points"
- connected by "edges"

**edges**:
- AKA "links" or "lines"
- connect "vertices" to each other

- there are multiple types of graphs:
**undirected**:
- edges connect vertices "symmetrically":
- any vertex can connect to any other vertex equally

- groups of connected vertices within an undirected graph are called "connected components" or "components"

**directed**:
- edges connect vertices "asymmetrically":
- relationships between vertices can only be established depending on which vertex is establishing the relationship -- relationships in graphs
*aren't necessarily reciprocal*