emo

it's definitely the way it is sung. You can sing a lyrics of an emo song into a pop or rock genre anytime(^^,)

I think that's up for debate.
It's mostly in the way that they sing. Whiney, crying vocals are not always emo. You would know by the hair. haha. An example of this would be the band Hawthorne Heights or From First to Last. Terrible stuff right there.
Sometimes the band doesn't even sing all whiney and babyish, but their lyrics are very depressed and dumb. An example of this would be the band Emmure. Look them up.. Emo lyrics without the typical emo voice. The music is very heavy hardcore with deathcore breakdowns. Alright stuff right there.

I think it's a combination of the two.

I would say neither, it's the style. The music & lyrics combine to get the message across - communcation!

From what I've heard, true emo is only a scene. It really has nothing to do with hairstyles and clothes. The lyrics are usually known for being sensitive well sort of, if you count acts of domestic violence. But most emo kids like being categorized by their outerwear, makeup, and hair. I think ten years from now they'll say 'What was I thinking?'.

By the way, emo is short for 'emotional' - I think that says it all!

know the real history of emo

emo came from hardcore and for emotive hardcore not emotional.