# Tree Arity (Binary, Quinary)

## What is tree arity?

Arity is how many children descend from a parent node in a tree. The most common implementation is the binary tree. Trees can have any arbitrary arity depending on the specific use case however. Why does it matter in Merkle Trees though?

## Why does it matter in a Merkle Tree?

When updating Merkle Trees on chain it can result in significant gas costs depending on the depth of the tree. To decrease gas costs a solution is to implement a SNARK friendly hashing functions that produces less constraints with higher arity. PoseidonT6 namely is one such function

<figure><img src="/files/H8ORGQFdkxIPqBqeBnGs" alt=""><figcaption></figcaption></figure>


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