API
Pronunciation: AY-pee-eye
Also written as: API — Application Programming Interface
A defined set of rules and protocols that allows software applications to communicate with each other. In editorial contexts, 'API' is always uppercased and the acronym is preferred over the full form after first mention.
Full Definition
An Application Programming Interface (API) specifies the methods, data formats, and conventions that developers use to interact with a software component, library, or service. APIs can be public (open to external developers), private (internal only), or partner-level. In documentation, the full form should appear on first use followed by the acronym in parentheses; thereafter the acronym alone is used. Editors should note that 'API' is not preceded by 'an' in most modern style guides—'an API' is technically correct phonetically but some house styles prefer 'a REST API' to avoid the article question. Misuse as a verb ('we API'd into the system') should be flagged.
Usage
Usage note: Always uppercase. On first mention, write 'Application Programming Interface (API)'. Do not use as a verb. Distinguish from SDK, which is a broader toolset.
In Context
- "The payment gateway exposes a RESTful API that developers query to initiate transactions." — Technical reference guide
- "Refer to the API documentation for a full list of supported endpoints." — Developer onboarding guide