The role of an application programming interface (API) in software development is to facilitate communication between different software applications. An API serves as an intermediary that allows developers to interact with external services and functionalities without having to understand the underlying code. This standardized interface enables the integration of various software components, promoting modularity and reusability. APIs are essential for building applications that require external data, such as retrieving information from databases or connecting to web services. They streamline development processes and encourage innovation by allowing developers to leverage existing technologies.