When an 11-inch ship stops looking like a battleship

When would a 21,000-ton ship with twelve 11-inch guns be classed as a heavy cruiser rather than a battleship?

By the end of the First World War, when capital ships were approaching 40,000 tons and carrying 16-inch or larger guns, that combination would look increasingly cruiser-like.

The answer treats warship categories as relative to their period rather than fixed by one gun caliber. A 21,000-ton, 11-inch-gun ship could once sit near the battle line, but it looks much smaller beside late-war battleships and battlecruisers with 16-inch and projected larger weapons. Classification follows the contemporary force hierarchy as much as any timeless definition.