I like to call the little ones "corvettes".
So do many Real World Navies... But they also tend to use Cutter for similar ships.
But note that CT has a few canonical patrol corvettes.
Adventure 7: Broadsword - A Zhodani Patrol Corvette, 600Td.
Adventure 6: Expedition to Zhodane - two different 600Td corvettes.
and CT also has a decanonized one:
The Ley Sector (Judges Guild) has a 400Td Corvette that is 2J2 4G P4 Model 5, 4x Triple turret 400Td... but it also has a 1000Td Colonial Fleet Cruiser.
For comparison, the IISS Ship Files has a 600Td Zhodani Patrol Frigate. J4 4G P4. It's a HG design...
And in MGT...
MGT AM Zhodani also has a 600Td Corvette.
MGT Scoundrel has a 600Td Customs Patrol Cutter.
Core has a 100Td Police Cutter
Originally, a Corvette was a fast warship too small for the line of battle, and usually smaller than a frigate. The late 19th C saw the term dropped... In WWII, it was almost synonymous with destroyer - almost, but not quite. Destroyers were typically torpedo-boat killers, and later (WWI on) torpedo armed ships, and corvettes were specifically anti-submarine.
A sail-era cutter was a small, fast single-mast and long bowsprit sloop, usually well under 20 guns, while a corvette was usually 20 guns and 3 masts.
All three (Destroyer, Corvette, Cutter) are small warships in modern (post 1965) use, but note that frigates can be larger or smaller than destroyers now; the reasons are political, and thus off-limits. Some modern frigates are essentially light cruisers...
Age of Sail, it was (smallest to largest)... Cutter (single mast), Brig (2 mast), Corvette (Fast 3 mast), Frigate (6th rate, 5th rate), Ship of the line (4th, 3rd, 2nd, or 1st rate). Note that Cutters, brigs, and Corvettes, and Sloops were all typically under 20-guns. Sloop can be used as a collective for almost all warships under 20-guns... and essentially, is "7th rate"... Note that Captains commanded rates 1-4, Master & Commander for 5-6, and Lieutenant commandant for 7th rate (and occasionally 6th rate). The french naval ranks still retain this: Captain of Corvette (LtCdr), Captain of Frigate (Commander), and Captain of [ships of the line] (Captain).
There's a wonderful Sci-Fi wargaming tradition of Escort, Corvette/Cutter, Frigate, Destroyer, Lt Cruiser, Heavy Cruiser, Battlecruiser, Battleship being the sequence by size... but several reverse frigate and destroyer. Traveller is the odd-man-out, using just as muddled and confusing a mishmash as World War II...
