I know this might seem like a tiny thing to some people, but I really hate when people try to define the a-spectrums specifically as a "lack" of that type of attraction.
Like, that phrasing actually reeks of aphobia and allonormativity (consciously or not).
Asexuality is not a lack of sexual attraction, it's experiencing little to no sexual attraction. Aromanticism is not a lack of romantic attraction, it's experiencing little to no romantic attraction.
I do not experience sexual or romantic attraction, but I don't "lack" those things. Lack implies a deficiency, a sense of incompleteness or wrongness. To lack something means that you are lacking in it, and inherently assumes that's a bad thing. That might not be the intention, but the word "lack" is just so pathologizing that I just hate using it to describe something like orientation.
My orientation is not a problem or an absence of something, it's just what I am.
I am not lacking. I'm just aroace.