block (s.v. "Block"): A Block is the basic element of a Blockchain. It functions as a journal, recording a series of transactions together with a reference to the previous Block. A Block is chained to its preceeding Block by a cryptographic hash as a means of reference. Blocks contain an identifier for the final state after all transactions contained in it are validated. There is an incentive mechanism that provides incentives to generate new Blocks ("mine Blocks") that comply to the rules of Ethereum by issuing a reward to an Account specified by the miner. (†2239)
block header (s.v. "blockHeader"): Relates a Block to its Block header data. The Block header data contains 15 pieces of information: 1. the parent hash, 2. the Uncle hash, 3. a beneficiary address, 4. a state root hash, 5. a transactions root hash, 6. a receipts root hash, 7. a log bloom filter, 8. the difficulty value, 9. the Block number, 10. the gas limit of the Block, 11. the gas used by all transactions in the Block, 12. a scalar timestamp in unix time() format, 13. a byte array containing extra data, 14. a mix hash and 15. the Block nonce. The property is functional because a Block can have only exactly one Block header. (†2245)
blockchain (s.v. "Blockchain"): An Ethereum Blockchain is a distributed database that maintains a continuously-growing list of records called *Blocks* secured from tampering and revision. Each Block contains a timestamp and a link to a previous Block in a Merkle tree structure. (†2240)
full node (s.v. "FullNode"): A Full Node is a participant in an Ethereum Network that keeps a record of the full Blockchain, the full state and engages in mining. (†2241)
genesis block (s.v. "GenesisBlock"): A Genesis Block is the unmined, deliberately created, very first Block in a Blockchain. It has no predecessors, i.e. no parent Block. (†2242)
lightweight node (s.v. "LightNode"): A light node is a participant in an Ethereum Network that does not completely do any of the following: store the complete Blockchain, store the complete world state, engage in mining. (†2243)
Merkle Tree (s.v. "ModifiedMerklePatriciaTree"): Merkle Patricia trees provide a cryptographically authenticated data structure that can be used to store all (key, value) bindings, although for the scope of this paper we are restricting keys and values to strings (to remove this restriction, just use any serialization format for other data types). They are fully deterministic, meaning that a Patricia tree with the same (key,value) bindings is guaranteed to be exactly the same down to the last byte and therefore have the same root hash, provide the holy grail of O(log(n)) efficiency for inserts, lookups and deletes, and are much easier to understand and code than more complex comparison-based alternatives like red-black trees. (†2244)
