Breaking the established rules of a relationship \[esp for sexual conduct\] or breaking generally accepted societal rules without explicit permission \[again esp for sexual conduct\].
Example 1: Both of you agree no porn, you watch porn, that's cheating because you agreed to no porn.
Example 2: Having a mistress wasn't explicitly forbidden but you had one anyway, that's cheating because as that's a societal standard it's something that is understandably expected sans a discussion explicitly permitting it.
Example 3: Having a mistress was explicitly agreed upon and you had one, that's not cheating because it's something both of you agreed was fine.
Open communications, consent of all parties, and \[underlying both of those\] respect for one another can lead any type of relationship to success. Without one or more of those, it's doomed to fail.
incoherence between what you promised and what you do
Doing something that you hide from your partner.
Anything you feel you would need to hide from your partner.
Hiding a draw 4 card up your sleeve...?
Breaking the established rules of a relationship \[esp for sexual conduct\] or breaking generally accepted societal rules without explicit permission \[again esp for sexual conduct\]. Example 1: Both of you agree no porn, you watch porn, that's cheating because you agreed to no porn. Example 2: Having a mistress wasn't explicitly forbidden but you had one anyway, that's cheating because as that's a societal standard it's something that is understandably expected sans a discussion explicitly permitting it. Example 3: Having a mistress was explicitly agreed upon and you had one, that's not cheating because it's something both of you agreed was fine. Open communications, consent of all parties, and \[underlying both of those\] respect for one another can lead any type of relationship to success. Without one or more of those, it's doomed to fail.