One page, for the reader who arrived without the vocabulary. Each entry gives the working meaning the book uses, not the full technical definition.
Anchor. The on-chain fixture that ties a commitment to a specific Bitcoin block: the transaction, the block header, and the proof that the transaction sits in the block. Once anchored, the commitment inherits the block’s place in time.
Branch and leaf. The book’s tree vocabulary. A branch is an identity that writes (a company, an institution, a coalition, a weather station), held together by one key and a chained history of Merkle roots. A leaf is a single signed observation anchored under a branch’s root.
Consistency proof. A short cryptographic receipt that a branch’s new root contains everything the old root contained, unchanged, plus new growth only. It lets any reader check that a branch is append-only. Certificate Transparency runs on the same pattern.
Inscription. Data written into a Bitcoin transaction so the chain itself carries it. The book uses the word for the act of anchoring a commitment on-chain at real cost.
Lightning. Bitcoin’s second layer for payments: a network of channels that lets value move instantly and at negligible fee, settling back to the chain when channels close. It makes payments of fractions of a cent economical.
Macaroon. A bearer credential: a cryptographic token that proves its holder has paid-for, unexpired access, without naming the holder. Issued by the payment rail and verified on the server, it carries its own expiration; the Lightning preimage is the proof of payment it is bound to.
Merkle tree. A structure that hashes many items pairwise up to a single root hash. Commit the root and you have committed every item beneath it; any single item can be proven against the root with a short path. It is how a thousand observations ride one inscription.
OpenTimestamps. Peter Todd’s protocol, running since 2016, that batches hashes into a Merkle tree and anchors the root on Bitcoin. It proves that a document existed before a given block, at almost no cost, without requiring trust in the calendar server.
Proof of work. The mechanism that makes Bitcoin’s history expensive to rewrite: miners burn energy to find valid blocks, and rewriting the past means redoing the work while the rest of the network keeps adding to it. The book leans on the consequence rather than the mechanics. Energy burned cannot be unburned.
Provenance. Where a datum came from, checkably: who signed it, when it was anchored, at what cost, and what history the signing key carries. On the tree, these facts are recorded in the substrate itself rather than asserted by the record’s keeper.
Sats. Satoshis, the smallest unit of bitcoin; one hundred million to the coin. The book’s unit of cost for inscriptions and payments.