Well dock in the context of "Landing ship dock"

An amphibious assault ship is a type of amphibious warfare ship designed for spearheading amphibious incursions of marines into enemy territories during an armed conflict, via launching either naval landings or air assaults and also by providing shipborne close air support and logistics for landed friendly forces. Such a ship is typically the capital ship of a dedicated fleet known as the amphibious ready group or expeditionary strike group.

Amphibious assault ships evolved from aircraft carriers converted for specific use as helicopter carriers, which, as a result, are often mistaken for conventional fixed-wing aircraft carriers. Like the aircraft carriers they were developed from, some amphibious assault ships also support V/STOL fixed-wing aircraft, and some latest models (e.g. China's Type 076) have catapult systems for assisted takeoff of fixed-wing light aircraft such as UCAVs and have a secondary role as drone carriers. Most modern AAS designs also carry landing craft with most including a well deck, usually at the stern, to support large LCACs (hovercraft) and LCUs, which can insert both infantry and combat vehicles directly onto land.

A landing helicopter dock (LHD) is a multipurpose amphibious assault ship that is capable of operating both as a helicopter carrier and as a dock landing ship. LHD vessels are built with a full-length flight deck similar in appearance to a light aircraft carrier to operate VTOL rotorcrafts such as utility/attack helicopters, tiltrotor aircraft (such as the MV-22 Osprey) and VSTOL fixed-wing aircraft (such as the AV-8 Harrier and the F-35B Lightning II), as well as a well dock for launching landing crafts and amphibious vehicles. Some recent designs, such as the Chinese Type 076 class, even support CATOBAR operations for light aircraft and UCAVs via aircraft catapults and arresting gears.

The United States Navy (USN) and the Royal Australian Navy (RAN) use the term as a specific hull classification symbol. Examples of this kind of ship include the USN's Wasp class, French Navy's Mistral class and ships of the Spanish Navy's Juan Carlos I class including those designs based on the class, such as the RAN's Canberra class. Other nations also use the designation for their vessels, such as the Republic of Korea Navy for its Dokdo class. The Type 075 and Type 076 classes of the People's Liberation Army Navy (PLAN), though only regarded as amphibious assault ships in their native China, are considered LHDs in NATO reporting names.