There's a question of viability that I think matters. An unborn human starts as a clump of cells, develops a brain and heart but is still not viable on its own, and then if all goes well it becomes viable by the time it is born. It's human all the way through, but different people draw the line on abortion in different places along the path to viability.

Slaves were always completely viable. Bringing them up in a discussion about abortion is a strawman argument.

If you use viability as a guideline, you do bring into the debate people who were viable, but who through disease or accident are no longer viable. Should they be 'abort-able'? I think if the rules around abortion were flexible enough to apply to these people as well, they'd probably be solid enough to satisfy almost everyone's moral and legal sensibilities.

I may regret posting this since it's getting far off the topic of language, but the discussion is an interesting one.

I don't think the line is drawn on the viability spectrum. A baby isn't viable until a month before it comes out of the womb, and that's a stretch. So I don't think this is a matter of people disagreeing with what constitutes viable because there really can't be any debate about that. I would argue that "potentiality" is a better term here.

The arguments, at their core, revolve around the fact that you have two living things who's interests may not be aligned. It's a question of who's interests will be favored.

Now, you can feel what you want about this, I don't want to get into a policy argument, but let's not dance around the issue, abortion is about the conflict between two abhorrent options.