Navies traditionally grouped their fighting vessels into distinct tiers based on the number of heavy guns they carried. A first-rate ship of the line carried the most armament and required the largest crew, while lower rates designated smaller frigates and sloops. The system determined everything from the commander's rank to the vessel's assigned tactical role in a fleet.
Heard on the job
She was built as a third-rate but got cut down to a frigate after the refit.
Insider tip
The term survives in general English as first-rate or second-rate, long after the naval classification system fell out of use.