How does one invent a spell?

[kempermentor]

No: HPFGUIDX 135346

Allie wrote:
> So here is what I have been wondering for a while:  how does 
> one "invent" magic, more specifically spells, charms, curses, etc?  I 
> can understand how a potion might be invented, mixing various magical 
> ingredients together, but not spells. 
> 
> Take for example, Snape's sectumsempra.  Did he first decide that he 
> wanted a spell that would have that particular effect, and then set 
out 
> to discover the incantation and wand motions that would create it?  
Are 
> spells something that already exist and just need the correct words 
to 
> unleash them?  And what, exactly, is the difference between a charm 
and 
> a spell?


Kemper now:
I've read other people's comments on the difference between spell and 
charm, but for the beer in me, I can't remember....

As far as Snape's ingenuity, Yes, I think his intention of the outcome 
came prior to the incantation/wand movement.

Personally, I think creating a spell would be easier than creating a 
potion:
1. you have an intention.
2. you research latin based words of power, you combine a few and you 
test on rats or wormtails.

Or it could be something else entirely.