Here are the most common prefixes you’ll run into:
- SS – Steam Ship (or Steamship). Powered by steam engines. This covers most of your classic liners, such as Titanic, Olympic, Lusitania, and Empress of Ireland.
- MS – Motor Ship. Powered by diesel engines rather than steam. Hans Hedtoft falls into this category.
- MV – Motor Vessel. Essentially the same idea as MS. Different countries and companies preferred one abbreviation over the other.
- RMS – Royal Mail Ship. This wasn’t about propulsion at all. It meant the vessel carried mail under contract to the British Royal Mail. That’s why Titanic was RMS Titanic, not SS Titanic, even though she was steam-powered.
- HMHS – His/Her Majesty’s Hospital Ship, like HMHS Britannic, after she was converted.
- HMS – His/Her Majesty’s Ship, used by the Royal Navy.
- HMT – His/Her Majesty’s Transport, used by the Royal Navy.
- PS — Paddle Steamer.
- RMSP — Royal Mail Steam Packet.
- RFA — Royal Fleet Auxiliary. Useful once the military side grows.
- USNS — United States Naval Ship. Different from USS
- HMT — His/Her Majesty’s Transport or Trawler, depending on historical context.
- TS — Training Ship. Again, context can matter.
- SV — Sailing Vessel. Not steam
- MTS — Motor Turbine Ship.
- MT — Motor Tanker.
- LST — Landing Ship, Tank.
RMS – Royal Mail Ship
Not a type of engine, but a ship under contract to carry the British Royal Mail.
Examples:
- RMS Titanic
- RMS Olympic
- RMS Lusitania
- RMS Mauretania
- RMS Queen Mary
SS – Steam Ship (Steamship)
Powered by steam engines.
Examples:
- SS Edmund Fitzgerald
- SS Daniel J. Morrell
- SS United States (before later conversion terminology became common)
- SS Pacific
MS – Motor Ship
Powered by diesel engines rather than steam.
Examples:
- MS Hans Hedtoft
MV – Motor Vessel
Essentially the same as MS. Different companies and countries preferred different abbreviations.
Examples:
- MV Explorer
- MV Sewol
- MV Doña Paz
- MV Wahine
HMHS – His Majesty’s Hospital Ship
A ship serving as a hospital ship for the Royal Navy.
Example:
- HMHS Britannic
HMS – His Majesty’s Ship
A commissioned Royal Navy warship.
Examples:
- HMS Hood
- HMS Dreadnought
- HMS Victory
USS – United States Ship
A commissioned ship of the U.S. Navy.
Examples:
- USS Cyclops
- USS Johnston
- USS Arizona
SMS – Seiner Majestät Schiff (“His Majesty’s Ship”)
Used by the Imperial German Navy.
Example:
- SMS Seeadler
One thing to remember is that these prefixes don’t describe the size of a ship. They identify the ship’s role, ownership, or method of propulsion. As technology changed, so did the prefixes. Steamships became motor ships, mail contracts disappeared, and naval prefixes varied from country to country. Understanding these abbreviations is a simple way to learn a little more about every ship’s story.