Everyone has that one friend who never stays single for long. As soon as they break up with one person, they're on to the next, switching partners so often it can be difficult to keep up.

It can be whiplash-inducing, sure, but it also fits into a broader cultural pattern: most of us will experience several exclusive relationships over the course of our lives, especially with marriage rates are on the decline. As renowned psychotherapist Esther Perel has noted, "monogamy used to mean one person for life; now monogamy means one person at a time."

Still, most experts agree that there's a fine line between moving through a handful of serious relationships and engaging in "serial monogamy," as that endless partner-hopping is known. In fact, as Kinsey-certified sexologist Dr. Tara Suwinyattichaiporn argues, the pattern "can indicate challenges in forming healthy, stable relationships." But what, exactly, is serial monogamy? And what should you do if you suspect that you might be a serial monogamist? Here's what to know.

Serial monogamy is not defined by the number of exclusive relationships one enters into, but by how little time elapses between them. "Serial monogamy is the act of constantly moving from one relationship to another without taking any time at all to heal, grow, and reflect," explains licensed marriage and family therapist Adrienne L. Marshall. "It doesn't matter how long the relationship lasts; whether it's six months or six years, a serial monogamist will immediately jump right into another relationship after the previous one has ended."

On average, most secure people will spend anywhere from several months to several years single or casually dating after a significant relationship ends. A serial monogamist, on the other hand, is unlikely to go without a partner for more than a few weeks or months. In some cases, they may not break up with their current partner until they have another potential paramour lined up.

"It's common for serial monogamists to not have been single for more than a couple of months at a time since their teens," notes Sophie Roos, a licensed sexologist, relationship therapist, and sexual health expert.

"While it may seem obvious to family and friends, many people are unaware that they are indeed serial monogamists," explains sex therapist Dr. Shamyra Howard. Here are other common signs: