It seems like a foolish question that has a perfectly obvious answer. But if it was such an easy inquiry, then why all the drama around it? That's the easy one. Cheating is a major relationship rocker because it has to do with the murkiest thing life has to offer: human interactions and relationships.

So, what's cheating? How about a text message that says nothing more than "Lunch?" Or a voice mail that says, "Just wanted you to know I was thinking about you." Or how about an email that says, "How r u? Miss u. C u later?” Can words even be construed as cheating?

It's all relative and that's what makes cheating such a common and sticky predicament. The text about lunch could be far more insidious than the much more intimate sounding VM, depending on the sender, the receiver, and intent.

And what about acts? Are soft lips brushed against a warm cheek cheating? How about a handshake held two seconds longer than usual? Kissing? Hugging? Arms linked? Hands held? Thighs patted? Backs scratched?

Same goes. Who's doing it and whom it's being done to, along with the "why," are what determines whether what's going on is innocent or not so much. In some cultures, full body hugs and full-on mouth-to-mouth kissing are perfectly acceptable among friends. In others, they are considered as unacceptable as the sex act itself.

Cheating is not about one certain act or even a group of acts. It's about agreements and trust. One man's cheating is another girl's friendly greeting. So, how do we know and what do we do to protect ourselves and our relationships?

To my mind the answer is easy, and somehow that's what makes it so complicated. Talk to your partner. Seriously. Talk to your partner.

Are you OK with my going out with friends of the opposite sex when you're not there? Do you consider kissing cheating? Would it bother you if I exchanged flirty messages with a colleague when we both know it's just for laughs?

Although lots of folks like to make the rules for other people, the truth is that only the couple themselves can establish the rules for their relationship.

You don't have to like it. But that's the key to real and lasting relationships -- sharing the feelings you have and deciding as a couple how you will or will not act on them. When you are in a monogamous marriage, actually having sex with another person is usually a pretty clear "do or die" kind of line. But anything short of that lives in the land of murk when it comes to fidelity.

So talk about it. Tell her you think your boss is cute. Tell him you have kind of thing for your assistant. Once it's out there, it'll seem a heck of a lot less scary. And know that it's perfectly normal to be attracted to other people and even to engage in some innocent (or not so innocent) flirtation if your partner is OK with it.

The happiest and most successful couples I know are the ones who lay it all out there. No secret longings. No hidden email accounts. Just healthy conversations and acts between mutually consenting adults. The only thing that is never up for discussion is lying. That is a deal breaker across the board.

For the most part, we know when we're cheating. But if you feel like you might be walking the line, ask yourself -- would it be OK if my partner saw this or heard this or walked in on this? So many of us are so afraid of losing our partners and yet so unsatisfied that we choose the low road to get our needs met, knowing darn well we're betraying someone we love.

It's no wonder really. Affairs are rampant and many people in the public eye are the primary offenders. So it can be easy to say to ourselves, "Everybody's doing it. It's normal. So I will too." But being deceitful, especially to someone we love, is never OK. People arrange their relationships in all sorts of ways, from living apart to having multiple partners to being celibate to scheduling sex with their partner. The key is that it works for all those involved. Honesty is really the only thing a relationship must have.

Cheating is selfish. Talking about your needs and how to fulfill them is not. Mature love is about reality, not fairy tales. So, forget the facade and make a date with your partner for a heart to heart about what makes your heart skip a beat, because nothing is sexier than being in rhythm with whomever you choose to love.

Jenny Block is a freelance writer based in Dallas. She is the author of "Open: Love, Sex, and Life in an Open Marriage." Her work appears in "One Big Happy Family," edited by Rebecca Walker and "It’s a Girl: Women Writers on Raising Daughters," edited by Andrea Buchanan. Visit her website at www.jennyonthepage.com or check out her blog at wwww.jennyonthepage.blogspot.com.