The term is applicable to naval ships and large civilian vessels.
[1][2][3][4] Large ships are very complex and may take five to ten years to build.
Improvements based on experience with building and operating the lead ship are likely to be incorporated into the design or construction of later ships in the class, so it is rare to have vessels that are identical.
Nevertheless, building copies is still more efficient and cost effective than building prototypes, and the lead ship will usually be followed by copies with some improvements rather than radically different versions.
Ship classes are typically named in one of two ways; echoing the name of the lead ship, such as the Pennsylvania-class battleships, whose lead ship was USS Pennsylvania,[4] and the Olympic class, whose lead ship was RMS Olympic, or defining a theme by which vessels in the class are named, as in the Royal Navy's Tribal-class frigates, named after tribes of the world, such as HMS Mohawk.