French officer grades retain the sailing navy's categories of ship-of-the-line, frigate, and corvette captain. Capitaine de vaisseau corresponds to the Royal Navy captain, capitaine de frégate to commander, and capitaine de corvette to lieutenant commander. A modern warship can therefore carry several officers whose formal titles include captain while everyone still understands who commands the vessel. Each grade also indicates the scale of independent command for which the officer is prepared. In the age-of-sail example, a frigate captain taking over after a ship-of-the-line captain's death remained a captain exercising a captain's authority, even though the new command exceeded the officer's usual grade.
Notable Point · 36:58-40:20
French captain grades preserve age-of-sail command
Ship-of-the-line, frigate, and corvette captain titles identify the level of independent command an officer is prepared to assume.