Kurumi thought for a moment and cocked her head to the side. "I thought Aguamenti was a charm, Professor." Sure, they had had a debate from the previous discussion of the spell, but a thought came to her that she hadn't brought up previously. "Aguamenti, in a sense, changes the behavor of the wand by 'conjuring' water from it. I mean conjuring in a very abstract sense and not literally." She paused for a moment. "You could compare this to Lumos which makes the tip of the wand glow - once again changing the behavior of the wand. In Aguamenti's case, this is not light, but a stream of clear, potable water to issue from the tip of the caster's wand."

Or was he also implying that Lumos wasn't a charm as well?

This certainly was an outside of the box way of looking at this particular charm, but somehow it made logical sense in her brain - even if they had not discussed the charm in this manner the previous class.