Romantic relationships are so complicated and nuanced, we're still inventing terms to describe them. A few years back, some genius coined ghosting and suddenly we could communicate in two syllables the trauma of unexplained radio silence. More recently, Australian psychologist Melanie Schilling introduced us to the concept of "micro-cheating," a phenomenon that gained steam when social media co-opted our lives, but probably dates back to the middle ages.

"Micro-cheating is a series of seemingly small actions that indicate a person is emotionally or physically focused on someone outside their relationship," Schilling told HuffPost Australia last year, prompting a viral explosion of follow-up articles. "You might be engaging in micro-cheating if you secretly connect with another person on social media, if you share private jokes, if you downplay the seriousness of your relationship to your partner or if you enter their name under a code in your phone."

Sound familiar? We've all been there. Whether you're with someone you really dig, or someone you want to spend the rest of your life with, there's no guarantee you won't micro-cheat at some point. Part of the issue is the infraction feels so minor and undefined (until now). Maybe you just trade cutesy emojis with a coworker on the regular, or maybe you bump into your ex and omit that detail of your day to your partner when you get home. It's not like you're cheating-cheating, or even "emotional cheating," which is basically when you're "brain-dating" someone sans sex. Micro-cheating is more subtle and easy to brush off, but it's definitely a thing. So how do you know when you're doing it?

"Secrecy is the tell-tale sign," Schilling notes. And keeping prolonged secrets from a partner can have consequences from minor trust issues to out and out betrayal.

So how do you know when you've crossed the line? "You cross the line if you think your partner would feel uncomfortable if they saw your actions," relationship therapist Tammy Nelson tells Cosmo.

Then again some partners are more threatened than others, and a little outside flirting doesn't make you horrible person, not does it always require a confession.

"We all need the freedom to have friends and to express our caring toward them, and if someone is threatened by something as minor as their partner writing "Happy Birthday" on their Facebook wall, then that might be something they need to work through in a bigger way," relationship expert Margaret Paul tells MindBodyGreen.

In some cases, micro-cheating can actually be good for a relationship as long as it doesn't get too out of hand. If one of you is really bothered by the act of innocent flirting, then maybe there's an underlying issue that needs to be addressed before resentment builds up. On the flip side, exerting a little independence with a fleeting wink (virtual or not), can add a spark to your relationship. There's even some psychological studies that suggest outside flirting can enhance your sex life with your partner, by elevating self-esteem and opening the door to more creative fantasies.

"We need a healthy mix of interactions to sustain our relationships," sexologist Megan Stubbs tells The Lily. "It's unhealthy for our partners to be our entire lives."

Not everyone is on board with that theory, however. "Although micro-cheating may not be physical cheating, it's certainly testing the borders of emotional cheating," relationship expert Susan Winter warns in an interview with The Independent. "Flirting is flirting. And flirting is the act of fanning a spark that can easily spread to a flame."

Keep in mind, this concept of micro-cheating assumes a certain expectation of monogamy that some critics find a bit austere.

"It implies that feeling the tiniest attraction to anyone else is a red flag — a notion so at odds with normal human functioning that it sets a standard no relationship could ever meet," TheGuardian's Oliver Burkeman writes.

Certainly, every relationship is different, and the terms of that relationship should be something you decide together, free of outside judgement. So maybe you're down with monogamy but you both allow a little equal-opportunity side flirting. Are you still micro-cheating if, say, you don't immediately tell a charming stranger you're taken? Not necessarily. Though, according to Bustle, there are some serious forms of micro-cheating that tread on plain cheating—like keeping an active dating profile when you've agreed to be exclusive or listing an outside crush under a fake name in your phone.

It all comes back to Schilling's framework of secrecy—if you're hiding something from your partner, it may be time to consider the real reason behind it, for better or worse.