"Oh, it's not about which words, it's about how you say them. Like, uh," she marks her place in her book and closes it. "I don't know if you can even hear the difference, like, I could, but I'm relevantly magic--watch." She speaks a word that sounds like crystals tumbling in a rushing stream. Nothing happens. She makes the exact same sound again, and the book jumps into the air, leaping off her lap and tumbling halfway across the room.

"Whoa! That was so cool! It sounded the same to me both times though."

"Thanks! Yeah, I--haven't exactly made a study of phonology or anything, but when I've tried describing the difference to unaltered humans before it hasn't made much sense. Like a difference in tone without actually corresponding to a change in frequency."

"My mind jumped to wondering if it's like making a different facial expression but I don't think you did that either."

"Yeah, and if it were like that it'd be different in my other form and it's not."

"You can make imaginary facial expressions. With an imaginary third face."

"That is weird and not impossible but I think not accurate. It definitely feels more like doing something with my voice than my face." 

"Humans definitely can't do it?"

"No idea, I've never been able to coach a human to pronounce the sounds well enough to tell. But humans can write Correspondence sigils and get effects, even if the effects are usually fire, so, probably not definitely."

"Inconveniently all my human noisemaking is done internally so I can't make changes to it the way I can swap out my eyes, at least absent an anatomy tutorial."

"It is so inconvenient that I'm not masochistic enough for vivisection."

"Magical girls who really need to do internal organ stuff do transparent skin, usually, but it's pretty hacky."

"And I think the larynx is behind a bunch of other stuff besides skin."

"Yeah, major hassle. I was going to say 'I'll figure it out if I get an inconveniently located cancer' but presumably you can just glow at me."

"I can just glow at you! Didn't you say cancer was a disease? Do diseases have locations?"

"Cancer does! Usually, at least, I guess a blood cancer is sort of everywhere. Cancer is when some cells - we're made of trillions of tiny cells - mess up their mechanisms for dividing only when it's a good time, and start doing it constantly, and create tumors and divert resources to do more of that."

"I know about cells from the science textbook. That sounds like a weird disease, how does smog cause it?"

"I am not a doctor but I think it damages cells in a way that some of them survive but with cancer-causing errors? Sunburn does this too."

"...Sunburn. Huh. I wonder if this is a thing I've never heard of because we don't have it or because I live in a giant underground cavern."

"Most cancer isn't caused by sunburn, just some skin cancer."

"No, I mean, I'd never heard of sunburn before."

"That's probably because you live underground, yeah."

"I mean it could also be different? Grandfather is not a mindless ball of fire. But it could be not-different which would raise questions for me like why does Judgment-light burn people who have never even died or anything."

"I think a bunch of stuff would have to be different to prevent sunburn. Some animals can see the frequency of light that burns people, for instance."

"...Why is there a frequency of light that burns people?"