The actual body of a function, where the detailed processing statements are written, is termed as function ______.

The term for the actual body of a function where detailed processing statements are written is "Implementation." It's in the implementation that you provide the logic and functionality for the function. The other options have different meanings: Prototype is a declaration of the function, Definition is a broader term encompassing various aspects of a function, and Signature refers to the function's name and parameter list.