system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If black holes are just stars with a higher density which prevent light from escaping then, why aren't they referred to as a subcategory of star but instead a fundamentally different object?

Also, can black holes be formed from star collisions such as a binary star system not orbiting correctly? Or is it only possibly during supernova?

EDIT: Seems that for whatever reason I was under the impression that simply adding matter into a regular star would cause its "edge" to become its event horizon (although this makes no sense by itself) and that fusion would still occur within this. For some reason I could not think of a black hole as a singularity with a event horizon proportional to its mass, and was instead thinking that it was purely its size; I didn't take into account that even as a star, more density would have to occur for it to become a black hole, not just adding mass. Also the point that black holes aren't filled with hydrogen anymore and that if anything they would be composed of heavy elements, although even that wouldn't be the correct way of saying it.

Thank you to everyone, first time posting on this subreddit.
gpt
If you're going to assume that, then you have to assume everything in space is basically the same. Asteroids are just smaller planets, planets are smaller stars, stars are smaller black holes...

At some point, some things just fundamentally ARE different.