What counts as cheating; any thing that both partners do not or would not agree to. If you are not willing to do or say something in front of your partner, it is cheating. You are doing some thing that would betray their trust in you. Is it any less harmful to cheat emotionally verses physically? It is easer to justify to yourself that becoming emotionally involved with someone is not the same as being sexually intimate and is not cheating. When you are giving parts of yourself that you should be sharing with your partner to some one else it is cheating. This means, time, attention, emotional sharing, or physical contact.
Every couple or relationship has rules. The expectation is that both people are working with the same set of rules. This is not always the case. If every one played by the same rules there would be no market for websites like Ashley Madison, http://www.ashleymadison.com/. It is a web site that lets people who want to cheat find others who have no problem being the one they cheat with. Couples should discus what each other expect the rules to be for their relationship. Once the boundaries have been set, if one crosses them, it is cheating.
This is very important because if you are in a casual relationship with no expectations of monogamy there is no cheating even if both of you are sleeping with some one else. Although most people expect to have the traditional monogamous relationship, that isn’t the norm for others. Polygamy, swingers and open relationships seem to be on the rise, or at least more in the open then it was in the past. This opens unusual but very individual definitions of what is cheating and what is not.
Polygyny, http://en.wikipedia.org/wiki/Polygamy, is one man having more then one wife. Polyandry is one woman having more that one husband. Polygamy is having many wives and many husbands at one time, more like a group marriage. It can also been interpreted in a broad sense to mean any form of multiple mating. Would it be seen as cheating to pursue some one with intent of including them into the marriage of many? Or would it be cheating to pursue some one without intent to marry them? What set of rules or boundaries would this type of relationship have?
Swinging, http://en.wikipedia.org/wiki/Swinging, or the swinging lifestyle can be defined as non-monogamous sexual activity, treated much like any other social activity that can be experienced as a couple. Swinging activities occur when a married or otherwise committed couple engages in sexual activity with another couple, multiple couples, or a single individual. There are a lot of different rules set by couples, individuals and groups who are involved in this lifestyle. Each set of rules as individual as each person involved.
Open relationship, http://en.wikipedia.org/wiki/Open_relationship, or polyamorous relationship is a relationship in which participants are free to take other partners. There are quite a lot of people who enjoy the stability and image of being a married couple but want the freedom of being single. This is a very complicated arrangement and very difficult to balance even with some very clear expectations and boundaries.
Only you know what you consider cheating and it is your responsibility to let your partner or partners know where the boundaries are. Boundaries can be from one extreme to another. I know one lady who feels her husband is cheating on her if he looks at porn. Another had an open relationship and the only boundary they placed on each other was that they both always knew the when, where and who the other person was sleeping with. She came home early one evening and found her husband in bed with one of their lovers. She felt he was cheating, even though they both had a sexual relationship with this woman. Why, because the rule was that she should have been told that they were getting together that day. That they did not tell her betrayed her trust in him and her. Ironically the same woman she found with her husband was also the woman I found with my then boyfriend, with whom I thought I had a long-term traditional monogamous relationship.
No matter what the boundaries are in a relationship, it is the breaking of trust that does the most harm. That is what defines cheating. As long as you are doing something that betrays your partners trust it counts as cheating.