Glossary — Data Nexus

Forty-five terms an owner is expected to already know, written the way we would explain them on a first call: what it means, the formula if there is one, a worked example in real numbers, and the mistake that makes the number wrong. The last part is the reason this exists — the definitions are available anywhere.

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01/Unit economics

Unit economicsWith formula: What one unit of the business earns and costs, measured so that the answer to “should we sell more of this” is arithmetic rather than opinion.
CACWith formula: Everything spent to acquire customers in a period, divided by the number of customers that spending actually produced.
Marginal CACWith formula: What the next customer costs rather than what the average one cost — the only version of CAC that answers whether to spend more.
LTVWith formula: The contribution a customer produces across their whole relationship with the business, discounted for the fact that it arrives later.
LTV : CACWith formula: The ratio of what a customer is worth to what they cost — a sanity check on the model, not a target to optimise.
CAC payback periodWith formula: How many months of a customer's contribution it takes to earn back what they cost to acquire.
Contribution marginWith formula: What is left of a sale after every cost that exists only because the sale happened.
AOVWith formula: Revenue divided by the number of orders that produced it — the simplest lever on unit economics and the most volatile.
Churn rateWith formula: The share of customers who stop buying in a period, and therefore the reciprocal of how long a customer lasts.
Retention rateWith formula: The share of a cohort still active after a given interval — the same fact as churn, read from the surviving side.
Cohort analysis: Grouping customers by when they arrived and following each group separately, so that changes over time are visible instead of averaged away.
ROASWith formula: Revenue attributed to advertising divided by the advertising spend — a channel efficiency ratio, not a profitability one.

02/Demand and conversion

Lead: A contact who has given permission to be contacted about a specific thing. Not a customer, not a prospect, and not a metric a business should be run on.
MQL and SQL: Two agreed thresholds on the same contact: one that marketing will vouch for, and one that sales has accepted and is working.
Pipeline stage: A named position in the sales process defined by something the buyer did, not by how the seller feels about it.
Conversion rateWith formula: The share of a defined population that completed a defined action — meaningless until both the population and the action are stated.
Funnel: An ordered model of the steps between first contact and purchase, used to locate where people stop rather than to describe how they think.
Attribution: The rule that decides which touchpoint gets credit for a sale — a modelling choice, never a fact.
UTM parametersWith formula: Tags appended to a link so that analytics can tell where a visit came from — useful exactly to the degree that the naming is disciplined.
Session, user, event: The three units analytics counts in, each measuring something different and none of them a person.
Bounce rate and engagement rate: Two mirror metrics for whether a visit went anywhere — and the definition changed underneath everyone when analytics moved to GA4.
Vanity metrics: Numbers that rise without anything else improving — followers, impressions, likes — and which, when bought, actively damage the account that carries them.

03/Product and interface

User flow: The ordered path a person takes through a product to complete one goal, including what happens when it goes wrong.
Information architecture: How the content and functions of a product are named, grouped and nested — the structure a person navigates before they read anything.
Jobs to be done: The framing that a customer is not buying a product but hiring it to make progress in a situation.
Wireframe, mockup, prototype: Three different artefacts, each answering a different question, routinely used as if they were three levels of polish.
MVP: The smallest thing that can be built to test the assumption most likely to kill the business — not the smallest sellable version of the eventual product.

04/Search and the web

SEO: Making a site findable by search engines for the questions its buyers actually ask — a structural property of the site far more than a list of tasks performed on it.
GEO: Being citable by an assistant that is assembling an answer, rather than merely rankable by an engine that is returning links.
Structured data: Machine-readable statements embedded in a page that say what its content means rather than how it looks.
Canonical URL: The one address a piece of content declares as its real one, so that every variant of it consolidates into a single entry rather than competing with itself.
Core Web VitalsWith formula: Three measurements of how a page feels to use — how fast the main content appears, how quickly it responds, and how much it moves while loading.
Black-hat SEO: Tactics that manufacture ranking signals rather than earn them — cheap to buy, effective for a while, and the penalty outlives the supplier.

05/Security

Two-factor and multi-factor authentication: Requiring a second proof of identity beyond the password — and the factors differ enough in strength that “we have 2FA” says almost nothing on its own.
Account recovery path: The chain of accounts that can reset each other's passwords — and therefore the real security level of every account in it, which is the level of the weakest.
SPF, DKIM and DMARCWith formula: Three DNS records that together decide whether anyone can send mail pretending to be your domain — and whether your own mail reaches the inbox.
Business email compromise: Fraud carried out through a real or convincingly forged company mailbox, usually to redirect a payment — and by value, the most damaging attack a normal business faces.
Password managers and passkeys: Two mechanisms that remove the human from the part of authentication humans are worst at — remembering secrets, and judging which site to give them to.

06/Access and continuity

Offboarding: The sequence that removes a departing person's access to everything, in an order that does not lock the company out of its own systems on the way.
Least privilege: Giving each person the narrowest access that lets them do their job, so that a compromised or departing account costs the least it can.
Named accounts and shared credentials: Access issued to a person rather than to a login everyone uses — the difference between being able to revoke one person and having to change everything.
Key-person risk: The number of people whose sudden absence would stop something important — and in most small companies the answer for the digital estate is one.
Digital asset register: A written list of every account, domain and system the business depends on, recording who owns it, who administers it, what it costs and how it is recovered.
Handover: The point at which a vendor's work becomes the company's property — defined by what is transferred, not by the project being finished.
Vendor selection and total costWith formula: Judging a supplier on what the work costs over its life — including the rebuild — rather than on the quotation.

Not because anyone was careless. The denominators drift, the definitions were never written down, and nobody has had a reason to check. That is what the audit is.

Start with an audit Discuss an engagement

The definition, andthe error attached to it.

Whether one more customer makes the company money, and how long it takes to find out.

What is counted between a stranger and a paying customer, and where the counting usually goes wrong.

The shapes a product is described in before it is built, and what each of them is actually for.

How a site is found, by a search engine and by an assistant assembling an answer.

The accounts a business is actually attacked through — mail, social, and the recovery path behind both.

Who can reach what, what happens the day they leave, and whether the company still owns its own presence when they do.

Most of these are wrong somewhere in your own numbers.