SS, USS, RMS, JS, TSS, GTS, NS, and of course, HMS. We've all seen or heard such letters in front of ship names, if only in fiction ("Star Trek's" USS Enterprise), historical accounts (the RMS Titanic), and scattered news stories. Sometimes, a ship prefix indicates what type of propulsion a vessel uses, like SV meaning sailing vessel. Sometimes it indicates what country or affiliation it has, like PCG for the Philippine Coast Guard or SSM for Schiff Seiner Majestät. When translated into English, that latter German prefix equals a very common prefix that the reader might have heard about more than others: HMS. HMS means His/Her Majesty's Ship. This is the designation for British naval vessels.   Prior to the 1800s, prefixes weren't a standard feature of any and all seafaring vessels. But when American engineer Robert Fulton designed the very first, passenger-worthy, functioning steamboat in 1807, the Clermont, there arose a greater need to distinguish various types of ships. The 1800s saw an explosion of steamships hit the waters, and it became important for mercantile and military purposes to know who and what was on the waters. This is when we see SS arise as a standard prefix meaning "steamship."  HMS, however, predates such happenings. There's some disagreement on the timeline, but we know that King Henry VIII founded the British Navy in 1546 and King Charles II (ruled from 1660 to 1685) gave it the name "Royal Navy." 1653 saw His Majesty's Ship Bristol (no abbreviation) hit the waves. Since then, numerous ships have borne the HMS moniker.                              As stated, the exact timeline for the development of the Royal Navy is a bit unclear. British history in the mid-1600s was an absolute mess of religious and political conflicts too complex to cover here, and encompasses its Civil War. But by 1660, things started to even out. Then, and a little before, is when we start reliably seeing ships designated "His/Her Majesty's Ship." His/Her Majesty's Ship Wakefield, for instance, was renamed His/Her Majesty's Ship Richmond in 1660 in the midst of ongoing conflicts between the English and the Dutch. Then in 1707, the Royal Scots Navy — Scotland's own Navy — got integrated into Great Britain's armed forces per the Acts of Union, which set the stage for the U.K.'s naval dominance in centuries to come. But, it wasn't until 1789 that we saw the first abbreviation of "His/Her Majesty's Ship" into "HMS" with the HMS Phoenix. That century saw the English pit themselves against the French for naval superiority and eventually coming out on top in 1805 after beating French emperor Napoleon Bonaparte at the Battle of Trafalgar. This victory presaged British superiority over the world's waves for the entirety of the 19th century, as its naval power defined its position as a global superpower and creator of the largest empire in world history. Any and all ships having the prefix HMS in their name took part in this history-changing venture, as vessels built for the Royal Navy.                             Because HMS vessels are military vessels, they tend to come to greater acclaim and notoriety than, say, Royal Mail ships — with the huge exception of the RMS Titanic, which yes, was a delivery ship as well as a passenger ship. HMS ships swelled in number during the 19th century, and many newer ships adopted the names of older, decommissioned, or destroyed ships. Royal Museums Greenwich lists some HMS ships in use during the 19th century, which includes names both cute and humorous as well as imposing and immense. We've got the HMS Victory, HMS Hercules, HMS Juno, HMS Bellerophon, and HMS Immortalite side-by-side with the HMS Midge, HMS Penelope, HMS Seagull, the strangely named HMS Inconstant, and the HMS Wallaroo. Certain HMS vessels rank amongst the most famous vessels to ride Earth's oceans. Take the HMS Indefatigable, a name stretching back to 1784 and used by six different vessels from wooden sailing ships all the way to a colossal, World War I-era, 23,000-ton steel battlecruiser. The HMS Indefatigable occupies the top-tier name list along with its sister ships, the HMS Implacable and HMS Indomitable. Then there's the HMS Queen Elizabeth, named after the long-serving first monarch of that name who ruled from 1558 to 1603, which along with its sister ship the HMS Prince of Wales rank as the largest Royal Navy warships ever. Finally, the HMS Dreadnaught was the Royal Navy's first nuclear-powered sub commissioned in 1963, amongst many, many more.  If you're still interested, check out what it means when you see "SS" on a ship.