system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why aren't gas planets with a rocky core (like Neptune is believed to be) considered rocky planets with a giant atmosphere?

Or why aren't all gas planets considered just floating atmospheres?
gpt
The astronomical definition of a "planet" does not specify whether the body must be only rocky, only gaseous, or some combination of the two.

Neptune's core is much smaller than its atmosphere by volume, so discussions of Neptune tend to focus on its more dominant characteristics, the gas atmosphere and very large ice mantle.