Have you ever experienced “love at first sight” with someone, only to come to realize the connection was more so a short burst of honeymoon-phase fireworks than an enduring flame? I sure have. I’ve also felt attracted to people who weren’t exactly long-term-relationship material, but I still felt compelled to sustain the connection. These types of issues call into question whether I can decipher whether a connection is rooted in chemistry or compatibility. And to be sure, that distinction can be telling

After a little bit of googling, I’m quite certain I can’t, in fact, judge whether chemistry or compatibility is more so in place, which has led me to wonder: What are the real differences? How do we tell the two apart, and how can mixing them up potentially impact our partnered relationships—for better or for worse?

What denotes compatibility in a relationship?

“As human beings, we are first and foremost animals, and instinctually we have a desire to procreate,” says relationship coach Alex Scot. “Chemistry is the initial physical response and attraction we have to a person.” If chemistry isn’t a clear-cut matter, though, how can you know for sure if you and a partner have it?  “It’s that pull we feel. It’s heat, intensity, and immediacy,” says Claire AH, matchmaker and owner of Friend of a Friend Matchmaking, of the je ne sais quoi element of a connection.

And fortunately, you can harness it by paying attention to a few physical indications. “Signs you’re experiencing chemistry with a partner or a potential partner are an elevated heart rate, dilated pupils, [a] rush of blood to your lower regions, or what many describe as ‘butterflies,’ as well as a desire to continue the conversation or connection,” says Scot. So if your palms are sweaty, you’re weak in the knees, and you’re nervous, you might be feeling the chemistry of the new relationship.

What about compatibility?

Compatibility is deeper and more logical than chemistry. “[Compatibility is about] the various elements of lifestyle, values, and goals that feel in line with one another and how that manifests in your interactions,” says AH.

Scot says some signs of compatibility include a couple’s ability to get along, negotiate, compromise, problem solve, set and respect each other’s boundaries, and work together as a team. “You get along, you’re on the same page, you make each other laugh, and you feel like you can be a part of each other’s lives,” adds AH. However, she warns that compatibility isn’t necessarily about having everything in common with your partner. Rather, “it’s more about feeling like you complement each other,” she says. So, no, you don’t need to have the same exact hobbies (although that can be nice, too). You mainly just need to align or mesh well to be together for the long haul.

So, chemistry or compatibility? How to decipher the differences

While chemistry is the desire to go towards someone, AH says compatibility is what makes us want to stay there. “Chemistry is what we look for initially; it’s surface-level—an instinctual desire that sparks relationships to begin. Compatibility, on the other hand, is the vehicle that carries the relationship through life’s curveballs and increases the romantic love or bond we feel for our partners,” adds Scot. “The difference is [also] that it’s much easier to establish chemistry than it is compatibility.”

“The difference is that it’s much easier to establish chemistry than it is compatibility.” —relationship coach Alex Scot

Wondering how to tell the two apart while you’re in the throes of a hot and heavy new relationship? Scot suggests trying this exercise:

• First, look at the relationship as an objective whole.
• Then, create a T-chart with compatibility on one side and chemistry on the other.
• List out under the appropriate category which events between the two of you are points for chemistry, and which are points for compatibility.
• Finally, assess your results.

Ideally, you’ll want a pretty even list. “If you realize you have a ton of chemistry events—sex, adventures, dates—to log but no compatibility events—problem solving, compromising, working together—then that is a clear imbalance,” Scot says.

How confusing chemistry for compatibility can potentially impact your relationship

“Mixing them up can be a detriment to someone’s mental, emotional, and even physical health,” says Scot. “If you keep prioritizing the warm, fuzzy butterfly feelings of chemistry instead of prioritizing stable compatibilities, you could potentially stay in toxic relationships for too long, make justifications for mistreatment, or slip into codependency.”

“A relationship that’s almost all chemistry can burn hot and then burn out,” says AH, noting that time is often an important deciding factor. “If you feel an instant connection but see it wane fairly quickly, that’s a good sign that there wasn’t the compatibility to back it up.” Think: quickly falling head over heels for someone then, sometimes painstakingly, realizing that things aren’t so ideal or sustainable once you get to know them on a deeper level. And that’s where she says the defining problem (or potential for issues down the line) lies: having far more chemistry than compatibility, or vice versa.

Ultimately, AH notes that chemistry and compatibility can—and do—coexist, and make for wonderful relationships. But time is often an important deciding factor in seeing if things will last. “If you’re really invested in following initial chemistry and want to build a relationship with anyone who sparks that in you, you might wind up dating people who don’t fit well into your life or what you want out of it,” she says. “Before chalking issues up to what can often be seen as fated elements, it’s best to spend a little bit of time exploring if there’s anything more to intense feelings, difficulty maintaining interest, or quickly fading connections.”

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