His mother named him Uchiha Sasuke, but his mother is dead, and that makes him feel he should be too.
Sometimes Sasuke thinks he is dead, because the world turns and he is still there, clinging to life like one who isn't alive.
He looked up death in Kabuto's dictionary. Death (n.) is the cessation of all functions of life in an organism; the stopping of the heart, the failing of the lungs - but it didn't help.
He wondered what Mikoto had thought at the cessation of all functions of life in herself. He wondered if she had known it.
He categorises all that he thinks into that which will help him kill Itachi, and that which will not.
To his disgust, the latter outweighs the former.