Infidelity 
To dream of infidelity forewarns of your inappropriate interaction opposite sex or that you will bear grim outcome of your actions. You might have guilty feelings due to your involvement in an illicit affair or a sexual relationship. Your dream may also suggest lack of content in your current relationship, thus making you desire an adventurous and more exotic sex life.
Adultery
To dream that you've committed adultery means that you could have sexual desires or be sabotaging yourself. This likely comes from the root of your subconscious mind. You could be drawn into an issue that is not within your best interest such as a legal situation.
To dream that your mate or spouse has cheated means that you have concerns about abandonment. You may sense neglect within your own relationship. You could also feel as though you're not living up to what others want from others.
To dream that you are cheating with your friend's friend means that you're probably feeling forsaken by your own self.
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