What is an Open API?

ProgrammableWeb, an online news and directory for web-based application programming interfaces (APIs) references more than 13,900 APIs, which is up from 6,000 registered APIs in May 2012. This phenomenal growth! The number one category of web APIS by far is Mapping with more than 4,500 APIs. This is more than Social, Mobile or Finance! Perhaps this is why over the last 6 months there has been considerable discussion in the Open Geospatial Consortium (OGC) concerning APIs: What is an API, is there an ontology for classifying APIs, does the OGC develop APIs, and so forth.