Shipyard
A shipyard (also called a dockyard) is a place where ships are built and repaired. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Dockyards are sometimes more associated with maintenance and basing activities than shipyards, which are sometimes associated more with initial construction. The terms are routinely used interchangeably, in part because the evolution of dockyards and shipyards has often caused them to change or merge roles.
Yard (sailing)
The yards represent a considerable weight high above the vessel's centre of gravity; to increase stability, especially in heavy weather, some means is normally provided to lower some of the yards when they are not being used to set sails. In nineteenth-century warships (where a large crew was available) this was generally by physically "sending down" the upper yards from the masts and storing them on deck--along with, in many cases, the upper sections of the mast itself. Merchant ships in the age of sail would also do this before sailing in the Southern Ocean. On modern tall ships the yards are not designed to be sent down on deck, but 'lifting yards' that can be raised and lowered along a short section of mast using a halyard are often used.