Ad Astra military ship types

For reference; in adopting terminology from the Age of Sail to the Age of Space, many of these labels have been abused and misused over the years.  Here's what I consider the various "classes" of ships in AD ASTRA.

Single person craft
I'm actually cheating just a bit; some of these "single-person" craft do actually have more than one person in them, either as passengers or as crew.  In military craft, that may often mean a pilot, a gunner, maybe a tail-gunner, and maybe a bomber.  A co-pilot is always welcome, although the smallest of these ships does not have them.  In general, these are for dog-fighting or bombing runs, or simply for local transport (the equivalent of a Cessna) but it is a very, very rare "single" person craft that has ether travel capability, so long distance travel is not an option.  The largest of these might be something like a big cargo airplane of today; the smallest are like single-pilot tiny planes.

Corvette
This is the first of the ships that I'm actually meaning to talk about.  Rather lightly armed and armored, corvettes are military craft, originally meant for convoy duty, blockade running, or patrol of relatively quiet areas.  Not meant to stand up in combat to any kind of significant ship of the line.  Many pirates and privateers use corvettes, because they are small, light, cheap, maneuverable, and require a small crew, which makes them ideal for attacking non-military targets like yachts, freighters or liners.  Although the Millennium Falcon is always called a modified freighter in Star Wars Expanded Universe material, I rather think that it's the perfect, iconic example of what I expect a corvette to look and behave like.  The ships that the characters in Old Republic get would all be considered corvettes by my book as well; even if in game they are given other designations.

The "Double Dub"—a nickname for the modified corvette Wayland's Wyrd, a privateer used by the iconics.

The big exception to this lack of suitability for line combat would be torpedo craft; corvette-style ships modified to carry a payload of an extremely heavy weapon (with minimal ability to fire) that rush up to larger ships, fire their payload to devastating effect, and then rush back to safety.

Frigate
Larger, with heavier arms and armaments and room for much more crew, the frigate is the "standard" military craft.  Not completely a ship of the line, but designed for almost any other military duty except for protracted broadside-style space battles.  This is the ideal pirate vessel for larger crews as well, and often come equipped with a significant complement of marines for boarding actions.  They also serve as escorts for larger ships, and can be effective torpedo craft hunters.

Cruiser
A cruiser overlaps somewhat with frigate and with battleship below; it is essentially a medium sized ship that is capable of "cruising" i.e., operating independently, for the most part.  Capable of a wide variety of tasks, from independent scouting and exploration, fairly heavy ship to ship combat, orbital bombardment, commerce protection, blockades, etc.  In famous sci-fi terms, the Enterprise would be the most famous cruiser I can think of.  This is really defined more by the role than by the characteristics of the ship itself; frigates can be light cruisers, and on the heavy end, they can be very similar in design to battleships; again, the main difference is role rather than design (although many ships are designed specifically to be cruisers as opposed to frigates or battleships.)

Battleship
These are very heavily armed and armored, large ships of the line.  Imperial Star Destroyers, while sometimes serving in the role of a cruiser, are the iconic battleship from science fiction.

Carrier
These are also large ships, but they have little (if any) armament on their own; rather, they are meant to carry large components of fighters and bombers.

Dreadnoughts
These are really big super-heavy battleships.  Darth Vader's Super Star Destroyer would be an example.

Commercial craft
One could make a similar progression for commercial craft from the smaller little schooners and brigantines to the fast-cargo transport jammers and clippers, with yachts and liners, container ships, and tankers cutting across those categories to some degree as well.  All of them are ether drive capable, regardless of size.