An API serves as the interface between different applications. The requestor automatically gets access to data, with the benefit that the source doesn’t have to know how the other system exactly works. Unfortunately, few organizations maintain their data for (free) external use by means of an API. Good examples are the Twitter-API (streaming), NewsAPI and GuardianAPI (batch requests).
This article is part of the project Periodic Table of NLP Tasks. Click to read more about the making of the Periodic Table and the project to systemize NLP tasks.