Ego (noun)

1. A person's sense of self-esteem or self-importance.
2. An inflated sense of one's own importance or abilities.
3. Freudian psychology, a person's sense of self and the unconscious emotions and desires that are derived from it.

Origin:

Late 16th century: from latin, literally "i", used by freud to mean the conscious self.

Examples:

1. His ego was bruised by the criticism.
2. Her ego wouldn't let her admit she was wrong.
3. His ego was so fragile that he couldn't handle any criticism.
4. Her ego wouldn't let her apologize.
5. The psychologist concluded that his ego was the root of his problems.