The window during which a submitted result or withdrawal can be disputed under a protocol's rules.
An optimistic rollup needs time for challengers to identify and contest invalid claims. That window helps explain why a standard withdrawal can remain pending even when the app felt fast. Its duration comes from the protocol, while services offering faster exits can introduce their own arrangements and dependencies.
IN THE WILD
"The transaction executed on the rollup, but the standard withdrawal is still inside its challenge period."
Bitcoin inputs are spent completely, even when the payment is smaller than their total value. Your wallet normally creates a change output for the remainder after the payment and fee. Without an output assigning that remainder, it becomes transaction fee instead; change isn't an extra charge.
IN THE WILD
You spend a 0.01 BTCUTXO to send 0.003 BTC. A change output returns the remainder after the transaction fee.
A designated block used as a reference point in a consensus process.
Ethereum's proof-of-stake system uses checkpoints in its process for justifying and finalizing chain history. Validator votes link these reference points across epochs. A checkpoint is therefore a consensus marker, rather than a backup file you download or a promise that every block carrying a familiar label is already finalized.
IN THE WILD
A network monitor tracks whether recent Ethereum checkpoints are being justified and finalized as validators submit their votes.
Extra information used to detect certain accidental changes in encoded data.
A checksum helps software notice mistyped addresses or damaged data. It is a consistency check, not a certificate saying a recipient is trustworthy. Ethereum's EIP-55 uses capitalization to carry checksum information, but an address passing the check can still belong to the wrong person.
IN THE WILD
Your wallet flags a typo in a checksummed address. A scammer's correctly checksummed address could still pass that consistency check.
An estimate of the asset units available to the market under a data provider's methodology.
Circulating supply tries to distinguish available units from allocations treated as locked or otherwise restricted. Providers can draw that boundary differently, including how they handle treasury holdings. This helps explain why two dashboards may show different figures for the same token without either using its stated maximum supply.
IN THE WILD
"These two dashboards disagree." One counts a treasury allocation as circulating, while the other treats it as locked.
This use of 'coinbase' has nothing to do with the exchange's customer accounts. It's a special Bitcointransaction that creates the allowed subsidy and collects transaction fees without spending ordinary earlier outputs. Its reward outputs must mature before they can be spent, unlike an ordinary received payment.
IN THE WILD
You inspect a block's first transaction and see the miner's reward output. That's its coinbase transaction, regardless of which exchange you use.
A wallet setup that keeps signing keys offline during ordinary storage.
Cold storage puts distance between signing keys and an internet-connected device. Transactions can still be prepared elsewhere and passed to the offline signer. It mainly reduces certain remote attacks; backup loss, a mistaken destination and authorizing a harmful transaction remain separate problems to handle.
IN THE WILD
You prepare the payment on a connected computer, then pass it to an offline signer that keeps the keys off that computer.
Assets pledged to support a loan or leveraged position.
Collateral gives a lending or trading system something to use if a position no longer meets its rules. In DeFi, contracts often track its value using price feeds and apply limits to what it can back. A deposit's market price can fall, so the same number of tokens may support less borrowing later.
IN THE WILD
You deposit ETH as collateral for a token loan, then watch the position’s health as ETH’s market price changes.
The difficulty of finding two different inputs that produce the same cryptographic hash.
A fixed-length hash has fewer outputs than all possible inputs, so collisions must exist. Collision resistance means finding a useful pair should be computationally impractical. It matters when a hash commits to a document: an attacker should not be able to substitute different contents with a matching digest.
IN THE WILD
An attacker wants a harmless-looking file and an altered file to share one digest, so the altered version can pass the same hash check.
The ability to combine existing programs or protocols as parts of a larger application.
DeFi apps can call shared contracts and use their outputs in another part of a workflow. That makes lending, swapping and other actions fit together without rebuilding every component. The connections also carry dependencies: a change or failure in one component can affect applications relying on it.
IN THE WILD
Your app combines a lending-pool action and a DEX swap within the same contract workflow instead of rebuilding either protocol.
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.