> For the complete documentation index, see [llms.txt](https://docs.n8n.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.n8n.io/integrations/builtin/cluster-nodes.md).
# Cluster nodes
Understand cluster nodes in n8n, and browse the cluster nodes library.
[Cluster nodes](/key-concept-glossary.md#cluster-node-n8n) are node groups that work together to provide functionality in an n8n workflow. Instead of using a single node, you use a [root node](/key-concept-glossary.md#root-node-n8n) and one or more [sub-nodes](/key-concept-glossary.md#sub-node-n8n) that extend the functionality of the node.
## Root nodes
Each cluster starts with one [root node](#user-content-fn-1)[^1].
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## Sub-nodes
Each root node can have one or more sub-nodes[^2] attached to it.
[^1]: Each n8n cluster node contains a single root node that defines the main functionality of the cluster. One or more sub-nodes attach to the root node to extend its functionality.
[^2]: n8n cluster nodes consist of one or more sub-nodes connected to a root node. Sub-nodes extend the functionality of the root node, providing access to specific services or resources or offering specific types of dedicated processing, like calculator functionality, for example.