Merkle Root
A single hash that fingerprints every transaction in a block, letting nodes verify data efficiently.
The merkle root sits at the top of a merkle tree. Transactions get hashed in pairs, then those hashes get hashed again, level by level, until one value remains. That value is the root, and it lives in the block header.
Change a single transaction and the root changes completely. This lets a light client confirm that a transaction belongs in a block without downloading the whole thing. Bitcoin and Ethereum both rely on merkle structures to keep verification cheap.
Related terms
A structure that hashes transactions in pairs up to a single root, letting you verify one without all.
HashA fixed-length fingerprint produced by running data through a one-way function; any change yields a completely different output.
BlockA batch of transactions bundled together, time-stamped, and cryptographically linked to the block before it.