# Patterns

Graph pattern matching sits at the very core of Cypher®. It is the mechanism used to navigate, describe and extract data from a graph by applying a declarative pattern. Inside a MATCH clause, you can use graph patterns to define the data you are searching for and the data to return. Graph pattern matching can also be used without a `MATCH` clause, in the subqueries EXISTS, COUNT, and COLLECT.

A graph pattern describes data using a syntax that is similar to how the nodes and relationships of a property graph are drawn on a whiteboard. On a whiteboard, nodes are drawn as circles and relationships are drawn as arrows. Cypher represents the circles as a pair of parentheses, and the arrows as dashes and greater-than or less-than symbols:

``()-->()<--()``

These simple patterns for nodes and relationships form the building blocks of path patterns that can match paths of a fixed length. As well as discussing simple fixed-length patterns, this chapter covers more complex patterns, showing how to match patterns of a variable or unknown length, find the shortest paths between a given set of nodes, add inline filters for improved query performance, and add cycles and non-linear shapes to path patterns.

This chapter includes the following sections:

• Primer - a short primer on how to get started with using graph pattern matching in Cypher.

• Fixed length patterns - information about node, relationship, and path patterns.

• Variable length patterns - information about quantified path patterns, quantified relationships, and group variables.

• Shortest paths - information about finding the `SHORTEST` path patterns.

• Non-linear patterns - information about equijoins and graph patterns (combined path patterns).

• Syntax and semantics - a reference for looking up the syntax and semantics of graph pattern matching.

The model data in the examples used in this chapter are based on the UK national rail network, using publicly available datasets.