"Human" (adjective) and "human" (noun)

 It is not uncommon for anti-abortion people to not understand that the word "human" has multiple meanings.

One meaning is just "biologically human," as in, for example, some biologically human skin cells. On this meaning, "human" is an adjective, and just because something is human--biologically human--doesn't mean it's wrong to kill that thing: for example, it's not wrong to kill some random skin cells.

Another meaning of "human" is a noun: "a human" or "humans." This use of human amounts to saying something like "person" or "human persons." Humans, on this meaning, are usually wrong to kill.

(There are complications though in that humans, on this meaning, don't usually seem to have a right to other humans' bodies, even if that means they will die; it is at least unclear what sacrifices anyone must make for other humans, meaning other people).

It's easy to see how these meanings differ. Consider a permanently comatose body, say of a beloved relative at the end of their life: we might say, "This body is human, but the human we knew is gone." The first use of "human" is an adjective; the second is a noun and we are referring to the person that used to be "in" in that body.

Perhaps this post and this graphic will help people better understand what "human" can mean and why the different definitions matter.

P.S. This was all reviewed in the classic 1973 article "On the Moral and Legal Status of Abortion," so this type of distinction has been known for at least 50 years. Almost any ethics class on abortion will review this article:

https://rintintin.colorado.edu/~vancecd/phil215/Warren.pdf