# Define

URL: /define · Id: `page:/define`

> How an API is defined: its Product, its operations, its Offer and the Wrapped Sources it reads, all as data.

An API is one [Definition](/reference/concepts#definition): its operations, their parameters, examples and posted rates, all written as data, with no code to deploy.

- [Define an API product](/quickstart): Define an API product from the records of a source or from a schema of Nouns, check it, and see every Interface the platform derives from it.
- [Product](/define/product): What a Startup sells; an API Product is one whose Definition declares operations.
- [Operation](/define/operations): One callable Verb on a Noun, named by its operationId, with its path, parameters, return schema, example, price and run.
- [Offers](/define/offers): What an Offer posts for an API, how its usage is counted, the caps it declares, and the rules it is checked against.
- [Wrapped Source](/define/sources): An outside source an API Product wraps, declared as one descriptor: its operations, Offer, meters, limits, tenancy and error map.