The first diesel-powered motorships were launched in 1903: the Russian (the first equipped with diesel-electric transmission) and French
Petite-Pierre. There is disagreement over which of the two was the first. Although merchant, commercial and private vessels have been inconsistently designated, the general official practice in the British Realm and former British colonies (whether today part of the Commonwealth or not) has been to designate the very largest (ocean going) vessels as "ships", the very smallest as "boats", and those intermediate steamers and other types too large to be considered boats and too small to be seen as ships, as "vessels". This is particularly true with naval vessels, where those large enough to be rated
ships (the Royal Navy designation for a commissioned ship, regardless of propulsion, being "
HMS" for "His/Her Majesty's Ship") are generally under the command of a ranked Captain (for a destroyer or above), or a Commander, while the smallest warships and intermediate vessels (such as trawlers and drifters) and large "boats" (such as
Motor Torpedo Boats prefixed
MTB and
Motor Gun Boats prefixed
MGB), and smaller launches (such as the
Harbour Defence Motor Launch prefixed
HDML, and
Motor Launches like the
Fairmile Type B prefixed
ML) might be commanded by a Commander, Lieutenant-Commander, Lieutenant, or Skipper (still smaller boats, such as the
Harbour Launch, prefixed
HL, might be commanded by a Warrant Officer, Petty Officer, or a senior rating). Although intermediate commercial and research vessels are generally prefixed MV (with internal combustion motors), RV (such as the
FRV Scotia of the
Fisheries Research Services), or similar, the Royal Navy has generally avoided using the word
vessel (rare examples being
Steam Tank Vessels and
Water Tank Vessels), instead prefixing such vessels based on the application they were designed for (not necessarily the application the Royal Navy used them for), such as
Admiralty Trawlers, prefixed
HMT ("His Majesty's Trawler"),
Admiralty Drifters, and
Admiralty tugs, all often designated as Auxiliary Craft. ==See also==