For as long as there have been relationships, there has been infidelity. And for as long as there has been infidelity, romantic partners have squabbled over what exactly counts as being unfaithful.

What counts as cheating?

Is watching porn cheating? What about flirting with a coworker even though you know nothing’s going to come of it? Where does a very close friendship cross the boundary into emotional infidelity? There’s no singular answer, of course, because there’s no singular relationship. So, we spoke with a range of experts — including a psychologist, relationship advisor, polyamorist, and divorce lawyer — to gain a deeper understanding of what defines fidelity and infidelity and how partners can draw boundaries responsibly. RELATED: 10 (Commonly Overlooked) Signs That Your Spouse Is Cheating On You Here’s what they had to say.

1. According to a psychologist: Cheating is anything involving a third party that violates the agreed-upon boundaries of a relationship.

“Generally, infidelity is considered to be an act involving a third party that violates the standards or boundaries of a relationship between romantic partners. More specifically, I would define infidelity as a unilateral decision by one romantic partner to become involved with a third party that is motivated by a perceived or real limitation in the romantic partnership. Agreements about relationship boundaries can best be approached as an opportunity to learn together; namely, to explore desires, values, and limitations. Perhaps more important than discussing what a partner can or cannot do is to dialogue about what a partner may be hesitant to express. Shame and the fear of shame inhibit couples from expressing what they want, need, or desire from a partner or keep them from divulging what they feel is lacking in their relationship. A partner’s unilateral decision to meet his or her desires outside of a relationship often represents an avoidance of shame in terms of communication within the relationship. The only way to move forward is to understand what inhibits communication and find ways to have a healthy dialogue. Unfortunately, the focus is often centered on the shame experienced in one partner due to the other partner’s interest in someone else, who that other person is, and what they offer by comparison; or the shame of the partner who was involved in the infidelity. This obscures the myriad of issues that should have been addressed in the first place that might have been a way for the couple to learn their way further into the relationship. It is too late when people cannot look at the shame they felt in their relationship both before and after their broken bond.” — Mary C. Lamia, Ph.D., Psychologist RELATED: Before You Have An Affair, Remember This

2. According to a sex coach: Cheating is choosing to emotionally bond and grow closer to someone outside of your relationship than with your partner.

“Most people assume infidelity is physical, but the truth is that all infidelity starts with emotion. If we’re unhappy in our relationship, it’s natural to be attracted to others who make us feel good. For example, if there is a co-worker who treats us well, we’ll naturally be attracted to that person, not on a romantic level, but on a social level. The attraction isn’t necessarily physical either, but if our home life is negative because of marital conflict, we’ll naturally be drawn even more to this other positive person. Spending more time with the positive person is a respite from the negative emotions we feel from our partner. Emotional infidelity starts when we take these feelings too seriously and begin to have a crush on the person. Once we start to flirt and spend more time with them, a relationship develops that has romantic potential and this opens the door to physical infidelity. What went wrong here? It all started with our willingness to grow close to this other person who offers a respite from the native feelings we’re harboring for our actual partner. We made the decision to grow closer to that other person and form a personally intimate bond. Once this happens, it’s hard to backtrack because now you’re “all in.” From the other person’s point of view, you’re leading them on if you start to pull away. So then you’ll need to be honest to them about why you were growing closer in the first place, now they are aware of your marital difficulties at home and you’ve created an awkward workplace situation because this other person knows what’s actually going on. How to prevent this situation altogether? Communication is key here. We need to be open and honest with our partners and let them know what we’re not happy about. It takes compromise and effort to make any relationship work and proper communication to let each other know how we’re feeling. It’s never healthy for a relationship to start looking elsewhere for positive approval.” — Mayla Green, Sex Coach

3. According to a relationship counselor: Cheating is anything that breaches the boundaries of your partner and the relationship.

“I think what really counts as cheating in a relationship depends on what the couple decides for their relationship. What may be considered as cheating for one person, may be an act of betrayal for the next. For instance, some partners may see watching porn as no big deal, and may even partake in watching it together. However, for others that can be a major offense to the relationship. Others may look at cheating as purely physical, whereas some may feel even more betrayed by emotional cheating. I think a great rule of thumb for if it is cheating, is if it is a secret or not. Would you share what you are doing with your partner, or are you keeping it from them? If you are keeping it from them, then odds are you know they would not find what you are doing acceptable, and therefore you shouldn’t be doing it.” — Jordan Madison, MS, LCMFT

“Two things count: any alienation of affection without the partner’s consent and spending money without the partner’s consent. So, if you are spending emotional time with someone, particularly at the expense of quality time with your partner and your partner is upset about it, then you’re probably cheating. The good news for cheaters is that ’no-fault’ divorce has largely eliminated the discussion over who bears responsibility for a failed relationship. But, as someone who has seen a lot of relationships collapse, it all starts when one partner starts giving someone or something else more time than the other partner can handle. On the other hand, the law still has some strong opinions when it comes to money. This is because money is easy to quantify, unlike the precise amount of pissed-off your ex-friend might be. It’s also because when partners get mad at each other, they inevitably make the argument about money (and the kids, too, sometimes). Once you’re spending community money without your partner’s approval, you’ve cheated. You’ve taken something that belongs to both of you and used it for your own ends. If you’ve spent it on someone besides yourself, that’s even worse, because it’s not just selfish, it looks like you value that person more than your partner. What both these things have in common is betrayal. Someone feels betrayed, that their trust has been broken. Women know what I mean. Sometimes I have to explain to the guys. Has your wife ever taken some food or beer you were saving and given it to her friend you don’t really like? Has she ever thrown out your old letter jacket? How far you can go varies with every relationship, but once it gets to court, only the lawyers really win.” — Joseph Hoelscher, Managing Attorney, Hoelscher Gebbia Cepeda PLLC RELATED: 3 Reasons Your Husband Is Cheating On You, But Doesn’t Want A Divorce

5. According to a life coach: Cheating is finding your values outside of your relationship.

“This is a tricky arena where society has created a definition of infidelity, yet, I believe it is a personal definition. For some, infidelity could be watching porn; for others it could be having an emotional intimate relationship with someone outside the bounds of their spouse or significant other. Of course then for others it is the sexual infidelity. I help clients find their truth for themselves and define it, and then determine how they want to be in that, own it, and make amends for it, for themselves and their partners. One of the hardest struggles for many people is realizing that infidelity comes from a space of being misaligned in their own values. Something in their current relationship isn’t in alignment with their own values so they go seeking it elsewhere and then get caught up in an affair. If we would ask ourselves this one question, ‘What values are out of alignment for me in this relationship?’ I believe a much more healthy outcome would happen rather than infidelity.” — Rick Clemons, ICF Certified Life Coach

6. According to a polyamorist: Cheating is when you violate the trust within the relationship.

“I define fidelity as remaining faithful to the existing terms of the relationship. And an infidelity is a ‘cardinal sin’ or any ‘violation’ of the relationship. I think every relationship has, or should have, its own ’terms.’ For example, I’m not financially dependent on any of my partners. So I don’t have terms that expect them to make career or financial choices with my input. If my partner quit his job, or bought an expensive car, I wouldn’t see that as impacting our relationship. But if we had joint finances, were raising kids together, or had different terms of the relationship, I would consider it an infidelity if my partner took on debt, made a huge purchase, or changed his financial situation without consulting me. In monogamous relationships, often the ‘ultimate infidelity’ is having sexual or romantic experience with another person. (There’s also the concept of an ’emotional affair’ or ‘micro-cheating’ which implies that the experience doesn’t even need to be sexual or romantic; it just has to be intimate in any way to be infidelity). This sometimes — though not always — means that ‘cheating’ of this type is the worst thing someone could do, and therefore other things are not as bad. The assumption is that cheating is a huge blow to the relationship that either needs lots of work to heal, or can’t be forgiven and will end the relationship. But other things, like manipulation, cruel language, plain old unhappiness, sexual incompatibility, etc. don’t have the same sense of ’this is a huge betrayal of the relationship.’ It’s very important for me to point out that this is not how things work in all monogamous relationships. It is entirely possible for monogamous people to work out their terms of the relationship and not rely on assumptions about fidelity. However, monogamy makes it possible to let these assumptions go unexamined. You can be in a monogamous relationship based on existing societal terms. With non-monogamy, there is no predetermined ‘hierarchy of relationship sins’ to fall back on, so you have to establish what, for you, would be unforgivable vs. needs addressing vs. annoying quirk. In non-monogamous relationships, notions of fidelity are very specific to the relationship and the people in the relationship. Like I discussed above, it has to do with what the people involved have decided they would consider a betrayal or just a behavior they can’t tolerate in a relationship. For some people, it’s really specific; for others, it’s just. ‘if you stop making me happy, if you disrespect me, if you neglect our relationship’ — there might not be a need to identify specific actions that would be infidelity. For some non-monogamous relationships, it’s just not a useful concept.” — Zinnia, polyamorous writer and trauma worker

7. According to a relationship coach: Cheating is when you do something that goes outside the parameters your relationship abides by.

“In our modern culture, we tend to assume fidelity is the whole deal: sexual, emotional, relational, planning-for-the-future-together fidelity. But it isn’t so cut and dry. It varies from person to person because we all have different ideas about what’s okay and what’s not okay in a relationship. We get these stories from the ways we were raised—some may have been explicit, like advice from elders or peers, or it may be we picked up things implied by the media we consume. Or it could be culturally dictated. And the challenge is that we rarely have explicit conversations about this, a lot of it is assumed—and generally, we make a false assumption that what ‘we’ consider infidelity is going to be the same as what our partner considers to be infidelity. You might be totally okay with your partner having emotional relationships with other women because you assume it isn’t sexual. But maybe your partner is also attracted to women, and knowing that might change how you feel about her emotionally invested friendships. Or perhaps you’re okay with her having platonic relationships with other men, but she feels offended if you talk to other women online. There’s a mismatch there about what fidelity looks like. Ultimately, the parameters of fidelity have to be defined by the people in the relationship. I think the healthiest way to look at it is: being in integrity with the explicit agreements you make together. I think there’s this false notion that being in an open relationship is a ‘cure’ for cheating. Unfortunately, it isn’t. People in polyamory and other kinds of honest non-monogamous relationships are still capable of breaking promises, bending their agreements, and cheating. One of the definitions of polyamory is that it is non-monogamy done ‘with the full knowledge and consent of all involved’. So, if you’re in a polyamorous relationship, and you sleep with someone you met earlier that night at a party, and don’t tell your other partner about it in a timely manner, depending on how that partner sees it that could be an act of infidelity.” — Mel Cassidy, Relationship Coach RELATED: Can You Get Over Infidelity? 22 Ways Couples Can Heal After Cheating & Betrayal Seth Simons is a freelance writer and editor whose work has been featured in Medium, VICE, Yahoo Life, Adweek, Slate, Esquire, Vulture, Paste Magazine, Gothamist, Thrive Global and more. This article was originally published at Fatherly. Reprinted with permission from the author.