Nonce
A 'number used once' that serves two key purposes in blockchain: (1) In Proof of Work mining, the nonce is the variable miners change to produce a block hash below the target difficulty. (2) In transactions, the nonce is a sequential counter for each wallet address that prevents replay attacks and ensures transaction ordering.
“If your Ethereum wallet has sent 50 transactions, the next one will have nonce 50 (0-indexed). If a transaction with nonce 48 is stuck, nonce 49 and above cannot be processed until it resolves.”
Mining
The process of using computational power to validate transactions and add new blocks to a Proof of Work blockchain. Miners compete to solve a cryptographic puzzle (finding a hash below a target difficulty), and the first to succeed earns the block reward plus transaction fees. Mining secures the network by making it prohibitively expensive to attack.
Hash
A fixed-length alphanumeric string produced by passing data through a cryptographic hash function (like SHA-256). Hashes are one-way functions — they can convert any input into a unique fingerprint, but the original data cannot be recovered from the hash. Hashing is fundamental to blockchain security, mining, address generation, and data integrity verification.
Block
A collection of transactions bundled together and permanently added to the blockchain. Each block contains a timestamp, transaction data, a reference (hash) to the previous block, and a nonce. This chaining of blocks through cryptographic hashes is what makes the blockchain tamper-resistant.
Transaction Fee
A payment made to network validators or miners for processing and confirming a transaction on the blockchain. Fees incentivize block producers and prevent network spam. Fee structures vary by blockchain — Bitcoin uses a fee market based on transaction size in bytes, while Ethereum uses gas-based pricing. During congestion, fees increase as users bid for limited block space.