A glossary for independent product builders

Product and discovery

Activation — the first user action that demonstrates meaningful progress toward the product’s promised outcome. Signing up is not necessarily activation.

Assumption — something that must be true for a product or business plan to work but has not yet been established by evidence.

Concierge test — a test where the builder manually delivers part of the intended service to learn what customers value before automating it. Be transparent about the manual work.

Customer discovery — research into a target customer’s workflow, needs, and existing alternatives. It is not a pitch disguised as an interview.

MVP (minimum viable product) — the smallest credible product or service that can deliver a useful outcome and generate learning. It does not mean incomplete safety or quality.

Problem–solution fit — evidence that a proposed solution addresses a problem for a defined group. The phrase is often used loosely; state what evidence supports the claim.

Prototype — an artifact used to explore or test a design. It may be nonfunctional; label it clearly and do not imply that simulated features are live.

Business and growth

CAC (customer acquisition cost) — acquisition spend divided by new customers acquired over a defined period and channel. Include the costs you choose to count and do not compare unlike calculations.

Churn — customers or recurring revenue lost over a specified period. State the cohort, period, and whether the measure is logo, seat, or revenue churn.

Contribution margin — revenue left after variable costs associated with serving or selling to a customer. It is not the same as profit after all fixed costs and taxes.

Conversion rate — people who complete a defined action divided by a defined eligible group in a stated period. Always state the action and denominator.

Retention — the degree to which users continue to return or receive value over time. Choose a return event tied to the product’s real use cycle.

Runway — how long available cash lasts at a stated burn rate. It changes when revenue, costs, or funding change; it is not a fixed date.

Engineering and AI

Authentication (AuthN) — verifying an identity or account. It does not decide what that identity is allowed to do.

Authorization (AuthZ) — deciding whether a verified identity may perform an action on a particular resource. Enforce it at the server or data boundary.

Idempotency — a property where repeating the same operation does not repeat its effect, useful for retries in payments and background jobs.

Observability — signals such as logs, metrics, and traces that help explain what a system did and where it failed. Do not collect sensitive information just because logging is easy.

Prompt injection — untrusted content attempts to manipulate an AI system’s instructions or tool use. Permissions must be enforced outside the model.

RLS (row-level security) — database policies that restrict which rows a database role can read or change. It is not automatically safe; policies and privileged keys must be reviewed and tested.

Technical debt — future cost created by a shortcut or design choice. Some debt is deliberate; record what was traded away and when to revisit it.

Reading this wiki’s terms

Words such as “validated,” “secure,” “accessible,” and “profitable” are claims, not badges. Each needs a stated test, scope, and evidence. See MVP scope, business basics, and security review for the fuller context.