Alphabetical order has one structural weakness when the subject is a protocol. It files "nullifier" a long way from "note", and the first of those words is close to unreadable without the second. Spelling is a poor guide to a vocabulary whose 16 core terms were built to depend on one another.
So this glossary is grouped by what the terms describe. Sixteen definitions, one sentence of substance each, arranged roughly in the order somebody actually meets them. Every entry then points at the article in this series that owns the concept properly, because a definition is a handhold rather than an explanation.
Transparent, shielded, and the pools that hold them
Zcash sorts each unit of value into one of two visibility regimes, and nearly all of the vocabulary downstream of that split inherits its shape from the split itself. Three words carry the distinction between them, and getting those three straight is what makes the remainder of this list legible.
A pool is the accounting bucket that a given unit of value currently occupies. This is not informal terminology; the consensus rules constrain pool balances directly, and a proposal titled "Prohibit Out-of-Range Chain Value Pool Balances" exists specifically to stop any block from driving a shielded bucket below zero (source: ZIP 209). There are several pools, and their names, histories and differences belong to our guide to Zcash shielded pools, which treats them as its subject rather than as background.
Transparent describes value held in the transparent pool, where the payer, the payee, the sum and the timing involved are all published for anybody reading the chain. That is the visibility model most chains use by default, and if it is unfamiliar, our walkthrough of reading a transaction on a block explorer shows what "published" concretely means.
Shielded describes value held in a shielded pool, where those same three facts are encrypted and the transaction's validity is proved cryptographically instead of being demonstrated in the open. What that trade costs a user, and which side suits which situation, is the entire subject of our guide to Shielded vs transparent Zcash.
That pairing is the most load-bearing distinction in the protocol, which is also why it gets flattened into a slogan so often. It describes individual units of value. It does not describe the chain, and it does not describe you.
What a shielded payment is made of
Open any technical description of a shielded transaction and four terms arrive within a paragraph of one another. They form a chain in which each term only makes sense once the previous one does, so reading them out of sequence is most of what makes such paragraphs feel impenetrable.
A note is the unit of shielded value itself. It holds an amount and a recipient, and behaves roughly like a single unspent output on a transparent chain. Readers who have met the unspent output model already have the closest available intuition.
A note commitment is the cryptographic stand-in that gets published to the chain in the note's place. Commitments are what every observer sees. Notes are what only the parties to the payment see, and the gap between those two statements is where shielded privacy actually lives.
A nullifier is the unique marker revealed when a note is spent, and it exists to solve a problem that encryption creates: if nobody can see which note you are spending, nobody can see that you have already spent it. The protocol specification settles it by construction: exactly one valid marker corresponds to any given note. A repeat attempt emits a duplicate, and duplicates are refused (source: Zcash Protocol Specification). Our guide to Zcash shielded pools works through why that holds.
A memo is an encrypted message field carried inside a shielded payment and readable by the recipient alone. Its designers described the gap it fills plainly: a shielded payment otherwise tells the recipient an amount and almost nothing else, so "you don't learn anything about the sender or about the history of the money you're receiving, and you don't see the sender's address" (source: Electric Coin Company). The reference libraries carry it as a first-class type rather than as an afterthought (source: zcash_protocol). Its sizes, formats and uses are our guide to Zcash memo field's territory.
Addresses and keys
This group is where a reader is most likely to guess wrong, because every word in it is borrowed from ordinary usage and the borrowing is imperfect in at least one consequential respect. Five terms cover what you publish, what you hand over selectively, and what you never share with anybody.
A transparent address receives value into the transparent pool. A shielded address receives value into a shielded pool. Both are addresses in the ordinary sense our explainer on what a blockchain address is describes; what differs is which pool the arriving value lands in, and therefore what the world gets to see afterwards.
A unified address bundles several receiving options into a single string, so that a sender's wallet can use whichever one it supports instead of forcing the recipient to publish several addresses and guess. The proposal defining them is titled "Unified Addresses and Unified Viewing Keys" (source: ZIP 316), and our guide to Zcash unified addresses gives the mechanism its proper treatment.
A spending key is the secret that authorizes spending. It is the direct counterpart of the private key in the public and private key pairing that secures most chains, and it carries the same consequence: whoever holds it can move the funds.
A viewing key is the term with no clean equivalent elsewhere, and the one worth slowing down for. It grants the ability to see shielded activity without granting any ability to spend it, which is what makes disclosure to an accountant, an auditor or a counterparty possible at all. Our guide to Zcash viewing keys covers what a viewing key does and does not reveal, and that boundary matters considerably more than the definition does.
How the protocol changes
The final group covers the vocabulary of change. It turns up in every upgrade announcement. It runs through every release thread and every argument about the project's direction. Four terms account for very nearly all of it. The first is also the one most frequently misread by people quoting it.
A ZIP is a Zcash Improvement Proposal, the document format the project uses to "propose new features for the Zcash cryptocurrency and their rationale, specify the implementation details of the feature, collect community input, then document design decisions" (source: zcash/zips). A ZIP number identifies a document. It carries no implication whatsoever that the thing described was ever built.
A network upgrade is a coordinated, scheduled change to the rules every participant must follow, deployed through a ZIP of its own. A recent one is titled exactly that: "Deployment of the NU6.3 Network Upgrade" (source: ZIP 258). Our guide to Zcash network upgrades covers how upgrades are structured and why they are run this way.
An activation height is the block number at which an upgrade's new rules take effect. Block numbers are used rather than dates because a height is unambiguous to software while a calendar date is not.
A consensus rule is a rule every participant must apply identically for the chain to remain one chain. Software that stops applying one has stopped following the chain, an outcome much sharper than it sounds and closer to a chain split than to an ordinary bug. Who decides which rules change is our guide to Zcash governance and zips's subject.
What a glossary leaves out
Definitions are the cheapest thing in this entire subject, and being honest about their limits is more useful than adding another twenty entries would be. A one-sentence definition is a pointer to a concept rather than the concept, and three specific gaps are worth naming before you go any further.
The first is that knowing what a term does tells you nothing about whether it works. Knowing that a nullifier prevents double-spending does not tell you whether the construction is sound; evaluating that takes the underlying cryptography, not the vocabulary.
The second is that the words are load-bearing in ways one sentence cannot carry. "Shielded" covers several distinct pools with materially different properties. "Note" resembles an unspent output in some respects and diverges from it in others. A glossary that flagged every such qualification would stop functioning as a glossary, which is why the community's own reference runs to an alphabetical wiki page rather than a paragraph (source: ZecHub).
The third is the one that actually costs people money. Knowing what shielded means tells you nothing about whether your own holdings are shielded, because that depends on your wallet's defaults and on what you have done since. It is a question about your setup and your history rather than about the protocol, and the answer can differ from one balance to the next inside a single wallet. It sits alongside the broader habits covered in our guide to privacy basics. Treat these sixteen definitions as directions rather than destinations, and follow the routes.
The vocabulary that has been retired
Some of the words you will meet in older material describe things that no longer exist or no longer work the way the word implies. Recognizing them is more useful than defining them, because their main effect is to date the source you are reading.
Terms naming a specific pool generation are the largest group. Each pool had a name, and material written during its era uses that name as though it were permanent. When you meet one, the useful question is not what it meant but when the text was written, because the answer usually explains everything else about the page.
Terms describing the original node software are the second group. That implementation is being retired. Its documentation is still online and still detailed, so instructions written for it can send a reader down a path that no longer exists. Our page on the node transition covers what replaced it.
Terms from the setup ceremony are the third. That procedure was central to the launch, it generated a great deal of writing, and it was subsequently removed from the design. Material treating it as a current property of the system is describing history without saying so.
And terms borrowed from other privacy designs are the fourth. Mechanisms that mix inputs, or that hide a sender among decoys, belong to different architectures. Zcash does neither, so a definition borrowed from one of those and applied here will be confidently wrong.
How the vocabulary is organized underneath
Four categories account for nearly every term in this subject, and knowing which category a word belongs to tells you how much it can change and who can change it.
Consensus terms describe rules every participant enforces. They change only at an upgrade, at a specific block height, and the change is the same for everybody. A claim using one of these is checkable against the specification.
Cryptographic terms describe constructions and their properties. These change when the protocol is redesigned, which is rare, and their meanings are set by the mathematics rather than by any implementation.
Wallet terms describe what an application does. These vary between products, change whenever a developer decides, and a statement using one of them is true of some software rather than of the network.
Ecosystem terms describe organizations, funding arrangements and processes. These are the most changeable of the four and the most often quoted as though they were fixed.
Sorting an unfamiliar word into one of those four before looking it up saves more confusion than any individual definition does.
Terms that mean something different here
Half a dozen words carry a general crypto meaning and a narrower Zcash meaning, and reading the general one into a Zcash sentence is the most reliable way to misunderstand it.
Address does not identify an account here in the way it does on an account-based chain. It identifies a destination and, on the private side, a capability rather than a balance a stranger can look up.
Balance is not a chain fact for shielded funds. Your wallet computes it from material only your keys can read, which is why a wallet mid-scan can honestly report a figure that is not yours yet.
Transaction fee is set by rules about the shape of the transaction rather than by an auction for scarce space, which means the number is far more predictable here than the general usage suggests.
Upgrade means a consensus rule change that every participant has to adopt by a specific block height, not a software release you can take at your convenience. Software that has not adopted it stops following the same chain.
Key does not mean one thing. Spending, viewing and incoming-viewing capabilities are separate objects with separate powers, and handing over one of them is nothing like handing over another.
And private does not mean anonymous. It means specific fields are not published. What can still be inferred from timing, amounts crossing between the two sides, and who you dealt with is a separate subject entirely.
How to use a glossary without being misled by it
A definition is a starting point rather than an answer, and three habits keep it from becoming the second.
Check when the term entered use. Vocabulary on this chain has turned over more than once, and a term that was central four years ago may describe something that is now closed or superseded. Anything defined without a date is describing an unspecified moment.
Check whether the term names a rule or a product. Consensus rules apply to everyone and change only at an upgrade. Product features vary between applications and change whenever their developers decide. Confusing the two produces confident statements that are true of one wallet and false of the network.
And check whether the definition would let you predict behavior. A definition you can act on tells you what happens when you do something. One that only tells you what a word means will not survive contact with an actual transaction.
Where to check a definition against the source
Three sources settle nearly every term in this subject, and knowing which one to reach for saves reading the wrong document carefully.
For consensus vocabulary, the protocol specification is authoritative. It is long and dense and it is the document every other account is paraphrasing, so a term used there means exactly what it says there.
For process vocabulary, the numbered proposal repository is authoritative. Terms describing statuses, categories and deployment targets are defined by that process rather than by any implementation.
For wallet vocabulary, the software's own documentation is the only source, and it binds nothing beyond that product. A term defined there describes a feature rather than a rule.
When two of the three disagree, the ordering above is the one to trust, and the chain itself outranks all three when the question is what is actually enforced today.
Frequently asked questions
How does a note differ from a note commitment in Zcash?
The note is the actual unit of shielded value, holding the amount and the recipient. The note commitment is the cryptographic stand-in published to the chain in its place. Everyone reading the chain sees commitments; only the parties to a payment see notes. That gap is where shielded privacy comes from, rather than from any single piece of encryption. Our guide to Zcash shielded pools covers how commitments are organized on the chain and why the arrangement is built the way it is.
What does a nullifier do?
It prevents the same shielded note from being spent twice. Because encryption hides which note a transaction spends, the chain cannot detect reuse by inspection. Per the protocol specification, exactly one valid marker corresponds to any given note, so a repeat spend emits a duplicate marker and gets refused for that reason alone. The marker itself reveals nothing about which note produced it, which is the property that makes the check possible at all.
Is a viewing key the same as a private key?
No, and conflating them is the most consequential mistake in this list. A spending key authorizes spending, exactly as a private key does elsewhere. A viewing key grants visibility into shielded activity while granting no ability to move anything. They are separate objects with separate powers, and handing over the wrong one is not recoverable. Our guide to Zcash viewing keys covers which viewing keys exist and precisely how much each one discloses to whoever holds it.
Does a ZIP number mean a feature exists?
No. A ZIP is a document, and the repository hosting them describes their purpose as proposing features, specifying implementation details, collecting community input and documenting design decisions. Proposals sit at various statuses, drafts and withdrawn revisions among them. Citing a ZIP number establishes that something was written down, not that it was deployed. Checking a proposal's status line before repeating a claim about it takes seconds and heads off the mistake people repeat most often here.
Researched and written by the BloFin Academy editorial team with AI-assisted drafting. Primary sources are ZIP 209, the Zcash protocol specification, ZIP 316, ZIP 258, the ZIP repository, an Electric Coin Company post on the memo field, the zcash_primitives reference documentation, and the ZecHub community glossary. All facts independently verified against cited documentation current as of August 2026. This article defines terms and deliberately does not teach the concepts behind them; each definition routes to the article that does.