Interface

Interface is a definition of a role (a group of abstract actions). It defines what sort of behavior a certain object must exhibit, without specifying how this behavior should be implemented.

Interface - the place where independent and often unrelated systems meet and act on or communicate with each other [Webster`s Dictionary].

The interface is a connection between two pieces of electronic equipment or between a person and a computer.
The interface is a situation, way, or place where two things come together and affect each other [Cambridge Dictionary].

An interface is a surface regarded as the common boundary of two bodies, spaces, or phases.
Interface - the facts, problems, considerations, theories, practices, etc., shared by two or more disciplines, procedures, or fields of study [Dictionary.com].

Interface - the way a computer program presents information to a user or receives information from a user, in particular, the layout of the screen and the menus [Oxford Learner`s Dictionaries].

The interface is also called a contract. Every component upholds a certain contract (the signature of certain methods). That way, two components upholding a contract can communicate with each other without knowing how their counterpart works.

Sources:

Svetlin Nakov & Co Fundamentals of computer programming with C#: Sofia, 2013 - 1122 с. - 825

Interface. Webster`s Dictionary. Retrieved from: https://www.merriam-webster.com/dictionary/interface

Interface. Cambridge Dictionary. Retrieved from: https://dictionary.cambridge.org/dictionary/english/interface

Interface. Dictionary.com. Retrieved from: https://www.dictionary.com/browse/interface

Interface. Oxford Learner`s Dictionaries. Retrieved from: https://www.oxfordlearnersdictionaries.com/definition/english/interface_1?q=interface