Question: what is the difference between a heavy cruiser and a light cruiser?
Answer: The term light cruiser was given a definition by the London Naval Treaty of 1930. Light cruisers were defined as cruisers having guns of 6.1-inch (155 mm) or smaller, with heavy cruisers defined as cruisers having guns of up to 8-inch (203 mm). In both cases, the ships could not be greater than 10,000 tons.