Ship Abbreviations — Common Prefixes And Their Meanings

When you see or hear the names of ships, it’s common to encounter a set of letters listed before the vessel’s name. The USS Constitution, the HMS Bounty, the RMS Titanic, and the SS Lusitania are just some of the iconic ships named in this fashion.

To those unfamiliar, which would likely be most civilians, these letters may seem somewhat random. But they serve as a shorthand that helps to designate the type and purpose of the vessel. Knowing a ship’s prefix is valuable information for captains and other watercraft operators in the area.

However, not all ships use a prefix. This is especially true for small personal vessels, which rarely, if ever, bear a prefix. Similarly, many mid-sized vessels, such as ferries, do not carry one either. But on larger ships, they’re all but universal. 

Let’s discuss the most common prefixes and their meanings as it pertains to ship abbreviations.

SS — The Default Prefix

The original civilian ship prefix is SS, which is an acronym for “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 watercraft. They settled on the SS prefix in part because it had panache, similar to existing military prefixes.

It’s been a long time since most vessels ran on steam, and a majority of modern ships today run on diesel, fuel oil, natural gas, or even nuclear power. In comparison, a coal-burning steamship is slow, dirty, and inefficient.

The SS prefix has since evolved, now representing an acronym for “single-screw ship.” You’ll still see it in use today, although it’s not as common as it once was. A “screw steamer” or “screw steamship” is a somewhat archaic term for a steamship or steamboat. These are vessels powered by a steam engine that use one or more propellers (also referred to as “screws”) to propel it through the water.

The most important thing to remember is that SS is a civilian designation, and a ship bearing this prefix can serve just about any non-military purpose.

Ship terminology has changed in recent years, and the SS acronym has been in a slow decline. Still, it retains an important place in international shipping. While many prefixes are language-specific, SS is one of the few to be universally recognized, making it useful for ships that are primarily engaged in international trade.

SS vs. USS vs. HMS

SS is probably the most common designation you will see, and it’s often confused with “USS.” The fact that the two terms are nearly identical only makes that much more confusing.

In fact, 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, Air Force, and (presumably) Space Force vessels. Non-commissioned US Navy support vessels receive the special designation “USNS” (United States Navy Ship).

Another long standing military prefix is “HMS,” which is short for “Her (or His) Majesty’s Ship.” This is the British equivalent to USS and refers to all vessels of the Royal Navy. Most militaries worldwide use similar designations to refer to their military vessels and distinguish them from civilian shipping.

MV — Merchant Vessels

Outside of military and generic SS prefixes, “MV” is another common acronym. MV is short for “Merchant Vessel” and refers to any ship operating for business purposes, also known as “commercial vessels.”

An excellent example of a merchant vessel would be a cruise ship. They travel the waters of the world, stopping at attractive destinations along the way. People pay thousands of dollars for the privilege of going on a cruise, enjoying the ship’s entertainment, and even gambling at onboard casinos in some cases. Because these ships exist primarily to produce revenue, they’re considered merchant vessels, even though they’re not transporting cargo (aside from passengers, that is).

Conversely, military transport and supply vessels carry the USS designation, even though they’re carrying people and goods. The reason is that they’re doing so for military purposes, not for commercial purposes.

RV — Research Vessels

Another relatively common prefix is RV, which is short for “Research Vessel.” This might seem like a fairly niche category, but it’s surprisingly populated.

There are a variety of functions that research vessels serve. Some are utilized by researchers to prospect for oil or commercial fishing. Others are used for oceanographic and climate research. They can even be designed as icebreakers for exploring the Arctic.

As a result, research vessels are a diverse class. An icebreaker, for instance, is vastly different from a floating research platform on the Great Barrier Reef, yet both would use the RV prefix.

Other Common Ship Abbreviations

As we mentioned at the outset, ship prefixes are far from universal. However, US, Canadian, and UK civilian vessels use many of the same prefixes. Here are some of the most common:

  • MS is short for “merchant ship,” or sometimes for “motor ship.” It’s identical to the MV prefix.
  • FV translates to “fishing vessel.” While fishing vessels can legitimately carry the MS or MV prefix, FV is more specific and is beginning to see wider use.
  • SV is a “sailing vessel,” in most cases, but it is not always a civilian craft.
  • MY is short for “motor yacht.” It designates a large civilian recreational vessel that’s powered by a motor, not by sail.
  • MT is short for “motor tanker.” It typically refers to oil tankers but can also be used on tanker ships that carry any kind of liquid. This includes industrial chemicals and liquid natural gas.
  • TS translates to “training ship.” and is most commonly used for the Navy, Coast Guard, and other military training vessels.
  • CS is short for “cable ship,” a vessel that lays long-distance phone and data cables.
  • A PSV is a “platform supply vessel,” another specialized ship with a deck outfitted for resupplying an oil platform.
  • LB is short for “lifeboat,” which is self-explanatory.
  • An RMS, or a “Royal Mail Ship,” refers to any vessel under contract to carry letters for the Royal Mail. Incidentally, this is why the RMS Titanic bore the designation. In addition to its service as a passenger liner, it was also carrying mail between the UK and the US.
  • GTS stands for “gas turbine ship.” This can refer to any type of ship powered by a gas turbine, as opposed to diesel or some other method. However, it’s usually reserved for cargo ships.
  • NS is short for “nuclear ship.” It’s similar to GTS but refers to nuclear-powered rather than turbine-powered vessels.