Ah, so it simply refers to the curve. I've been a videographer by trade for some time, so I have a pretty healthy understanding of this stuff. It's just the chemical process that's new to me.
So I guess that's to say that tonality responds to light non-logarithmically? When I underexpose by 2 stops, my cloudy skies are just where I want them: a moody grey with spots of highlights with a feathery soft knee. My primary fear with overexposing is clipping those highlights, though with film I understand that highlights retain better across varying exposures than shadows do, correct? Meaning that overexposing will brighten the shadows disproportionate to how much it will brighten the highlights? I'm used to working with Log curves as part of the digital video workflow, where adjustments are impacted equally throughout the tonal range.
If your coming from video you are worrying about the highlights too much. Compared to video its almost impossible blow the highlights on film.