In starship classification, a heavy cruiser is a large multi-purpose starship. They are designed to perform and excel at a wide range of missions and tasks. The Heavy Cruiser has long been the primary ship of the Starfleet. They offer the best multi-mission platform and vessels of this type are the mainstay of their respective eras. They are similar to Explorers, with two exceptions:
1 - Heavy cruisers are intended for shorter duration missions than Explorers, usually 5 years or less.
2 - Heavy cruisers are built in greater numbers than Explorers.
The term heavy cruiser is sometimes used synonymously with battle cruiser. The Klingons once referred to the USS Enterprise as a battle cruiser. (Star Trek III: The Search for Spock)