An attempt to spend the same digital funds in two conflicting payments.
Copying a file is easy; making copied money count twice is the problem. A blockchain's rules and consensus mechanism settle on a history where conflicting spends cannot both succeed. Seeing a payment broadcast is therefore different from having confidence that its accepted history will stay in place.
IN THE WILD
Someone broadcasts two Bitcointransactions using the same UTXO. The accepted chain can include one of those spends, but not both.
Elliptic Curve Digital Signature Algorithm: a public-key method for creating and verifying digital signatures.
ECDSA is used by Bitcoin's legacy signatures and conventional Ethereum accounts with the secp256k1 curve. Signing uses a private key; others verify with the public key. Correct signature-nonce handling is critical. This cryptographic nonce is separate from Ethereum's transaction counter, which is also called a nonce.
An Ethereum Improvement Proposal: a document describing a proposed technical change or standard.
EIPs give the Ethereum community a shared format for discussing technical ideas. A proposal can cover protocol behavior, an interface or another standard, and its status tells you where it stands. Seeing an EIP number in a project announcement doesn't mean Ethereum has adopted the feature or that the proposal is final.
IN THE WILD
“This uses a new EIP” sends you to the proposal’s status and specification, not straight to assuming every wallet already supports it.
EIP-1559 changed how Ethereum execution fees are quoted and paid. A transaction can specify a maximum total fee and maximum priority fee, while the protocol sets and burns the base fee. This helps wallets estimate fees, but it doesn't make busy block space cheap or guarantee that every transaction gets included.
Transforming readable data into a form that requires appropriate key material to recover.
Encryption protects data contents, such as a wallet's stored key file. Hashing serves a different purpose and has no general decryption step. Using cryptography does not automatically hide blockchaintransactions: public records can remain readable even when a wallet's local files are encrypted.
IN THE WILD
Your wallet's local key file is encrypted; someone reading the file still needs the appropriate decryption material to recover its contents.
A measure of uncertainty that helps describe how unpredictable a cryptographic secret is.
For wallet keys, the useful question is how difficult they are to guess, not how impressive they look. Secure random generation supplies unpredictability. A long phrase chosen from familiar words by a person can be easier to predict than its length suggests, so length and effective entropy differ.
IN THE WILD
My favorite quote has plenty of characters, but the wallet generates key material from secure randomness instead of my predictable taste.
A group of slots used to organize consensus timing and related duties.
Epochs give a network a larger rhythm than individual block opportunities. Ethereum uses them for parts of validator scheduling and its checkpoint-based consensus process. The term isn't a universal amount of time across chains, so when a dashboard says “next epoch,” check the network's own schedule rather than assuming a fixed duration.
IN THE WILD
A staking dashboard says a change takes effect in a later epoch, meaning a scheduled consensus period rather than the next individual block.
An Ethereum standard that lets one contract manage multiple token types and transfer them in batches.
ERC-1155 can put different token types in one contract instead of requiring a separate contract for each. A game might use it for interchangeable resources alongside scarce items, with supplies defined per type. Batch operations can move several types at once, which is useful when an action involves a whole inventory.
IN THE WILD
A game uses one ERC-1155 contract for many identical wood tokens and a separate token type for a rare sword.
ERC-20 gives wallets and applications familiar ways to interact with many tokens. That shared interface is why a new token can appear in existing tools without each tool writing custom code first. It doesn't guarantee a token's value, authenticity or safe behavior, and unusual transfer rules can still surprise an app.
IN THE WILD
A wallet reads an ERC-20 balance and asks for a spending approval before a swap contract can transfer those tokens.
ERC-4626 gives wallets and apps a common way to request deposits, withdrawals and asset-to-share conversions. They can use one interface instead of adapting to every vault from scratch. The standard describes these interactions; it does not choose the vault's strategy or establish its security.
IN THE WILD
Your app asks the vault to preview the deposit: how many shares should these assets produce through its ERC-4626 interface?
The daily pick rotates automatically. Our initial collection was published on October 9, 2026. New words join on their publication date. Every concept includes a reference.