system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do clouds keep together?

How do clouds keep together and why do they not diffuse into a kind of sky-fog? Especially smaller clouds, which in my experience seem to start and stop quite abruptly.
gpt
Don't think of a cloud as an object, think of it as a region of air where certain conditions (temperature, humidity) are met. If for example temperature decreases as you get higher up, then at some point in that smooth continuum it will get cold enough for water to condense, and then you cross into the cloud region. It doesn't spread downwards unless something is cooling the air downwards.