How are spells actually cast in the ES universe?

Do people have to speak words? Or just think? I never really got it...

And why do people buy spells? How is that possible? Couldn't one person buy it teach it to all his friends?

Spells are cast by speaking the words needed to cast the spell. Hence why the "Silence" spell makes casting extremely difficult for mages when it's cast on them.

Technically, you're not buying the spell itself; you're buying the lessons needed to teach you the spell. If somebody wanted to teach his/her friends the spell for free, I imagine they could. It's generally more profitable to charge for the service, though.

On another note, it's possible some spells do not require speech. In 2920, a woman who summons a Daedroth says she think of the color red, the simplicity of it makes it helpful to summon creatures. In 'Breathing Water,' a character learns Alteration. They need to stretch their mind, learn to actually believe the impossible, it wears off when reality comes back to the player. How do you speak underwater?
How magic is cast is never explicitly stated, although multiple sources explain a little bit, it's just a big puzzle.

You mean you can't speak underwater? I do it all the time. :frog:

But yes, you're right, I forgot about those instances. It would seem that the majority of spells are cast by speaking the incantations, or at least up until the caster gains the proficiency to do so without actual speech. That's the way i've always seen it, anyway. :shrug:

From a gameplay persepctive, learning new spells isn't always something that costs money. During the TES IV Mages Guild quest line you learn at least three spells from non-player characters for no fee (Buoyancy, Weak Fireball, Wizard's Fury) and a 4th, optional, spell through a rather unique method (Fingers of the Mountain). Additionally, some spells can be cast while the player is silenced.

Such as?

Only "spells" I can think of are powers.

Anything marked as "Immune to Silence" in the CS. I doubt that there's any regular spells that have that flag marked, however.

Then how would Scrolls work?

I would guess that they function as "cast when used" enchanted item, except they are a single use item (like a potion).

If you actually click on a scroll in your inventory in the game, you will see that it has Daedric writing on it. One would presume that you would read this writing and the spell contained in the scroll is casted. Helpful for people who aren't mages and don't want to spend money learning the spell themselves.

I cast spells by going "pew!" When I need to cast lots of spells, I go "pew pew!"

Was this actually in Oblivion? I know Morrowind, but...

Hmmm....ya know, I can't remember. But even if it's not, I assume it'd still work the same way. Just imagine writing's on the scroll.