Protocols are a well defined theoretical concept in computing, and in other fields too. Protocols are an established system for communicating between two entities. HTTP, TCP, and UDP are well-know protocols that even have Protocol as part of the name. The concept has a well populated tag on Stack Overflow - Protocols. Sharing a common meaning between Code Review and Stack Overflow is generally useful. Contradicting Stack Overflow tag meanings is generally very confusing.
This tag was recently introduced as a tag on a Swift question. Protocols are a language structure that are similar to a class protoype, or interface, in other languages.
This meaning given to the Code Review Protocol tag is potentially confusing.
The current tag is protocols. Plural tags are unfriendly. Should it be the singular protocol?
Wikipedia links both Interface and Protocol as synonyms, with Protocol being the main name, and Interface being the synonym. Given that Code Review already has the Interface tag, and that Protocol is overloaded already, does it makes sense to use the language-independent tag interface for those uses of Protocol where the meaning is related to method prototypes, and to leave protocol for communication systems?