RMS

Royal Mail Ship

Royal Mail Ship , usually seen in its abbreviated form RMS, a designation which dates back to 1840, is the ship prefix used for seagoing vessels that carry mail under contract by Royal Mail...

 Britannic was an ocean liner

Ocean liner

An ocean liner is a ship designed to transport people from one seaport to another along regular long-distance maritime routes according to a schedule. Liners may also carry cargo or mail, and may sometimes be used for other purposes .Cargo vessels running to a schedule are sometimes referred to as...

 of the White Star Line

White Star Line

The Oceanic Steam Navigation Company or White Star Line of Boston Packets, more commonly known as the White Star Line, was a prominent British shipping company, today most famous for its ill-fated vessel, the RMS Titanic, and the World War I loss of Titanics sister ship Britannic...

, the company's third ship to bear the name. She was built by Harland & Wolff in Belfast

Belfast

Belfast is the capital of and largest city in Northern Ireland. By population, it is the 14th biggest city in the United Kingdom and second biggest on the island of Ireland . It is the seat of the devolved government and legislative Northern Ireland Assembly...

. She was launched on 6 August 1929. Like her running mate , Britannic was a motorship powered by diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s. She measured 26,943 gross tons

Tonnage

Tonnage is a measure of the size or cargo carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine, and was later used in reference to the weight of a ship's cargo; however, in modern maritime usage, "tonnage" specifically refers to a calculation of the volume...

 and was 712 feet (217 m) long. At the time of her launch she was the largest British-built motor liner. These two would be the only White Star motorships.