RMS, SS, MS and More: What Do Those Ship Prefix Letters Actually Mean?

You have probably seen ships with prefixes like SS or RMS, particularly on older ships. These aren’t random, they actually mean something.

The RMS Titanic is one of the most infamous ships in history. Everyone seems to know she sank after hitting an iceberg in 1912, but very few people will know why she was named like that.

The RMS Titanic was named after the Titans of Greek mythology. They were powerful deities. They were trying to convey a sense of the ship’s immense size and strength with that name.

The name was also chosen to match the other ship in the White Star Line’s Olympic-class fleet,. The Olympic was already sailing, and the sister ship Britannic launched later as the third ship in the class.

HMHS Britannic, also fitted the naming convention. The “ic” suffix was a naming convention for ships in the White Star Line.

What Does RMS Stand For?

RMS = Royal Mail Ship

Ships with the prefix carried mail/post under contract for the British Royal Mail.

• The term “RMS” has been used since 1840. In 1850, contracts were awarded to private companies to carry mail.
• Having the title “RMS” on your ship was seen as a mark of quality and speed, after all, the mail had to arrive on time.
• The mail is now sent by air as it is much faster.
  • The Royal Mail continues a form of this tradition on modern-day aircraft. British Airways is contracted to carry mail on some of its scheduled long-distance routes.
  • Aircraft on these routes are allowed to display the Royal Mail’s logo and crest on their fuselage.
• Royal Mail granted Queen Mary 2 the “RMS” prefix when she entered service in 2004 on the Southampton to New York route, a gesture to Cunard’s maritime history.
• Some ships still exist with the RMS prefix, but it is much less common now.

What Does SS Stand For?

SS = Steam Ship or Screw Steamer

• The original civilian ship prefix is SS, meaning “steamship.”
  • Back in the early days of powered water vessels, shipping companies wanted a way to distinguish their newer, faster steamships from older, slower sail and oar-propelled boats and ships.
• The SS prefix has since moved on, now representing an acronym for “single-screw ship.”
  • A “screw steamer” or “screw steamship” is an old fashioned term for a steamship or steamboat.
  • These ships are powered by a steam engine that use one or more propellers (also referred to as “screws”) to propel it through the water.
• You’ll still see it in use today, although it’s not as common as it once was.
• It was common for ocean liners in the 19th and early 20th centuries.

What About MS?

MS = Motor Ship

• This refers to ships powered by internal combustion engines (diesel/electric).
• It is more commonly used for modern cruise ships and cargo vessels.

Other Common Ship Prefixes You May See:

• HMS = His/Her Majesty’s Ship (used for British naval ships).
• RMHS = His/Her Majesty’s Hospital Ship.
• USS = is short for “United States Ship,” and its usage predates the usage of the SS prefix.
  • USS refers to any United States military vessel, including all commissioned Navy, Coast Guard, Army, or Air Force.
  • Non-commissioned US Navy support vessels receive the special designation “USNS” (United States Navy Ship).
• MV = MV is short for “Merchant Vessel”.
  • It refers to any ship operating for business purposes, also known as “commercial vessels.”
• TSS = Twin Screw Steamer
  • A vessel powered by two screw propellers.
• SY = Steam Yacht or Sailing Yacht
• FV = Fishing Vessel
• HMT = His Majesty’s Transport (often troop ships in wartime)
• LB = Life Boat
• RRS = Royal Research Ship.

The RRS Ship, Sir David Attenborough, was named after the world-famous naturalist. His legacy in British broadcasting inspired a love of the natural world over many generations.

In March 2016, the Natural Environment Research Council (NERC) launched an online poll asking the public to help name a new polar research ship.

The organisation said it was looking for “inspirational” suggestions for the government-funded ship.

Over 32,000 names were put forward, including:

• It’s Bloody Cold Here
• I Like Big Boats & I Cannot Lie
• What Iceberg?
• RRS Usain Bolt
• RRS Pingu (after the cartoon penguin!)

One particular name stood out like no other – RRS Boaty McBoatface. It received 33% of the total votes cast…

Originally suggested by a BBC radio presenter, James Hand, by the end of the poll on 16 April, Boaty McBoatface had 124,109 votes – 33% of the total vote.

Unsurprisingly, the Natural Environment Research Council (NERC) decided not to go with that!

Do Modern Cruise Ships Still Use These?

• No, not as much. Prefixes are now often left out in branding.
• Some still technically have them on official documents or registration paperwork.
• Cruise lines usually go for simpler ship names for marketing reasons.

Before You Go

Find out why we refer to ships as “she” here:

The Real Reason Ships Are Called “She” – Language, History, and Myth

Cruise ships and Ocean Liners are very different, they were designed for different purposes. Find out all about that here:

Cruise Ships vs Ocean Liners – Measurable Differences You Need to Know