Can an interface be considered a definition of a data type in programming languages?

In Go, an interface can be viewed as a definition of a set of methods that a type must implement to be considered compatible with that interface. Thus, an interface specifies behavior, not a specific data structure.

An interface does not describe specific fields or the internal structure of a type, only a set of methods that the type must have. Therefore, an interface can be considered a broad definition of a data type — an abstract type based on behavior, not structure.

Example:

// The Reader interface defines the Read method
interface Reader {
    Read(p []byte) (n int, err error)
}

// Any type that implements the Read method satisfies the Reader interface