Crypto Glossary

The blockchain trilemma states that a blockchain can optimize for at most two of three properties: scalability, security, and decentralization — and every design choice involves trading one for the others.

Consensus mechanisms enable distributed nodes to agree on a single state of the blockchain without a central authority — with Proof of Work using computational puzzles, Proof of Stake using economic bonds, and BFT variants using multi-round voting protocols.

Cross-chain bridges enable asset and message transfer between independent blockchains by locking assets on the source chain and minting representations on the destination — with trust models ranging from multisig committees (trusted) to light client verification (trustless) to optimistic verification with fraud proofs.

Ethereum has two account types — Externally Owned Accounts (EOAs) controlled by private keys and Contract Accounts controlled by code — each with a balance, nonce, and optional storage, forming the foundation of Ethereum's state model.

The EVM is Ethereum's deterministic, stack-based virtual machine that executes smart contract bytecode on every node identically — processing opcodes that manipulate a 1024-depth stack, volatile memory, and persistent storage.

Gas calculation in Ethereum involves summing intrinsic costs (21,000 base + calldata encoding), execution costs (per-opcode charges with cold/warm access distinctions), and memory expansion costs — with optimization techniques that can reduce contract gas usage by 30-80%.

Gas is Ethereum's unit of computational work — every EVM operation costs a fixed amount of gas, and users pay for gas using ETH through a dual fee mechanism (EIP-1559) where a base fee is burned and a priority fee tips the validator.

MEV is the profit a block producer can extract by arbitrarily reordering, inserting, or censoring transactions within a block — manifesting as frontrunning, sandwich attacks, arbitrage, and liquidations that collectively extract billions from users.

The mempool is each node's local pool of unconfirmed transactions waiting for block inclusion — where transactions are validated, prioritized by fee, and selected by block builders, making it a critical site for MEV extraction and fee market dynamics.

Ethereum nodes come in three types — full nodes (store recent state and validate all blocks), archive nodes (store complete historical state for every block), and light nodes (verify block headers only) — each representing a different tradeoff between storage requirements and query capabilities.

Ethereum token standards define common smart contract interfaces — ERC-20 for fungible tokens (currencies), ERC-721 for non-fungible tokens (unique assets), and ERC-1155 for multi-token contracts — enabling interoperability across wallets, DEXs, and dApps.

An Ethereum transaction is a cryptographically signed instruction from an EOA that changes the blockchain state — carrying a nonce for ordering, gas parameters for execution costs, and calldata for smart contract interaction.