On TikTok, there’s no shortage of tips for identifying a narcissist.

Look for “passive aggression,” one influencer suggested.

A narcissist is someone who “creates emotional dependency,” another said.

Being “extremely charming and charismatic — but kind of dead in the eyes,” one woman explained as she put on her makeup.

Decades ago, the term narcissism was rarely used outside of a clinical setting or a research study. Today, however, it has become a “catchall label for a broad range of disliked or frustrating behaviors,” said Virgil Zeigler-Hill, a professor of psychology at Oakland University in Rochester, Mich.

Narcissism, or the drive to feel special and unique, is a personality trait that exists on a continuum. Everyone has some degree of it; those who fall higher on the spectrum are typically egotistic and vain, but that doesn’t necessarily mean they have narcissistic personality disorder, or N.P.D.

There are specific criteria for diagnosing someone with N.P.D. Some of these include an unshakable need for admiration, a heightened sense of self-importance and a lack of empathy toward others. Those characteristics don’t come and go — they are persistent and typically lead to distress or interfere with relationships, work or other parts of life.

How well do you understand narcissism? See if you recognize any of the common myths below.

MYTH: The most harmful narcissists have a disorder.

Those who don’t meet the criteria for narcissistic personality disorder can still inflict pain on others and themselves. N.P.D. is rare: It is estimated to affect about 1 or 2 percent of U.S. adults.