Let’s start with the experts at wikipedia:

Diagnostic criteria (DSM-IV):  The essential feature of Narcissistic Personality Disorder is a pervasive pattern of grandiosity (either in fantasy or actual behavior), need for admiration, and lack of empathy that begins by early adulthood and is present in a variety of situations and environments.
In order for a person to be diagnosed with narcissistic personality disorder (NPD) they must meet five or more of the following symptoms:

  • Has a grandiose sense of self-importance (e.g., exaggerates achievements and talents, expects to be recognized as superior without commensurate achievements)
  • Is preoccupied with fantasies of unlimited success, power, brilliance, beauty, or ideal love
  • Believes that he or she is “special” and unique and can only be understood by, or should associate with, other special or high-status people (or institutions).
  • Rarely acknowledges mistakes and/or imperfections
  • Requires excessive admiration
  • Has a sense of entitlement, i.e., unreasonable expectations of especially favorable treatment or automatic compliance with his or her expectations
  • Is interpersonally exploitative, i.e., takes advantage of others to achieve his or her own ends
  • Lacks empathy: is unwilling or unable to recognize or identify with the feelings and needs of others.
  • Is often envious of others or believes that others are envious of him or her
  • Shows arrogant, haughty behaviors or attitude.

    • Now the greek bit:

    He was exceptionally proud, in that he disdained those who loved him.  As divine punishment Narcissus fell in love with his own reflection in a pool, not realizing it was merely an image, and he wasted away to death, not being able to leave the beauty of his own reflection.

    I guess it is not at all reassuring to women that “most [narcissists] are men.” Charles Zonor, in the November 29, 2010 New York Times reports that the new, draft DSM-V is eliminating the Narcissistic Personality Disorder. That, then, must be reassuring.

    Jonathan Shedler, a psychologist at the University of Colorado Medical School, said: “Clinicians are accustomed to thinking in terms of syndromes, not deconstructed trait ratings. Researchers think in terms of variables, and there’s just a huge schism.” He said the committee was stacked “with a lot of academic researchers who really don’t do a lot of clinical work. We’re seeing yet another manifestation of what’s called in psychology the science-practice schism.”

    Clinicians know it when they see it.