Researchers have long disputed the definition of "passenger ship". Definitions range anywhere between a ship with minimum cabin accommodations for twelve, to one accommodating fifty passengers; and from minimum gross tonnage of 2,500, to 6,000 tons. The original purpose of these vessels varied greatly. Many were originally cargo ships, and others were built to carry emigrants. Some were constructed specifically to be passenger cruise ships. As passenger ships, some only carried passengers seasonally, when not carrying cargo, for instance. Many of these vessels changed names and/or companies throughout their lifetimes. Some companies or passenger lines themselves were bought out and therefore took on new names.