Where do corvettes end and frigates begin?

Where is the line between a corvette, a frigate, and a destroyer?

The boundaries are blurred, especially as armament grows, which supports a clearer capability-based rating system.

The line between a heavily armed corvette and a light frigate is blurred. The same problem applies to heavily armed frigates and destroyers, whose labels can conceal overlapping capabilities. A River-class upgrade could therefore cross a naming boundary without producing an obvious new category. The ambiguity supports a clearer rating system based on capability instead of treating each type name as a fixed technical category.