What is diction? What some examples of it? I wrote a persuasive essay in my AP class, and my teacher wrote DICTION! everywhere.

Diction is the manner or style a person uses to express an idea.

Sometimes "diction" may be used to refer to the clarity of expression. I suspect that this is the intent of your teacher; perhaps he/she was trying to indicate that your ideas were not being expressed clearly.

Depleted of strength, Jose, perplexed by conflicting perceptions, suspended world consciousness until forenoon.

##color(white)("XXX")##versus

Tired and confused Jose slept until morning.