“With the Internet, we’re moving away from just physical ideas about infidelity and acknowledging emotional infidelity.” While there is no universally accepted definition, an Internet affair frequently involves intimate chat sessions and sexually stimulating conversation or cybersex, which may include filming mutual masturbation with a Web camera.

Several studies suggest that even when there is no in-person contact, online affairs can be just as devastating as the real-world variety, triggering feelings of insecurity, anger and jealousy.

Young sees more women who are online cheaters, in part, she says, because women gravitate toward erotic chats and webcam sessions while men often are drawn to pornography.

“The Internet is opening up these new ways of exploring your sexuality and that includes infidelity,” she says.

If there is no physical contact or actual sex, is it still an affair?

“It’s not just that you’re communicating with someone online but that there is a sexual or emotional nature,” says Katherine Hertlein, Ph D, an associate professor at the University of Nevada in Las Vegas who studies online affairs.

While men traditionally have been the more unfaithful sex, gender roles are reversing in some cases as more women experience cybersex.

“I think there is this bias that women don’t cheat for sexual reasons at all,” Hertlein says.

The typical affair used to start in the office and move to a seedy motel room, but the vast reach of the Internet has brought infidelity into many couples’ homes over the past decade.

The growth in steamy chat room conversations and cybersex also has triggered a rethinking of the meaning of infidelity.

Americans now spend as much time online as they do watching TV — about 13 hours a week.