What do you consider cheating?

it's human nature for a person to admire a person, even if they are already in a relationship, that is normal. There is nothing wrong with finding a person (other than your partner) beautiful, smart, attractive. The only time if becomes wrong is when you entertain the thought of being with that person and sacrificing your partner's feelings. :D

only thinking someone is not a cheating i think, It can be said cheating if both of you do the real things in real life. But sometimes just thinking about cheating will make you feel so guilty

Cheating comes in many forms it could happen in your mind or it could happen when you actually do something about it in physical form or there's some action originating from you. Cheating is like you think of others people beside your love ones and when you do it in actual world you already cheated. As for me cheating can only be called a cheat if there is some actual happenings or evidence that it really happened to both parties. Like for example if you are married and fantasizing about another girl. Then you tried to reach out for that girl and she return your affection and intentions...cheating already happens.

I agreed with your statement that if you are doing things with someone else that you should only do with your lover is cheating as cheating is adulterous and it is considered mostly partners or lovers. Indidelity and cheating are a betrayal of the expectations you have of your partner. Especially when it concerns his or her contact and relationship with another person. If you and your spouse have talked about this subject and you have openly expressed to him/her that you are uncomfortable with anythings, problem would solve there. The only way to define cheating and infidelity is if you feel your expectations of your spouse have been violated. When your expectations are not being met the emotional outcome is feelings of betrayal. If those are the feelings you are having, then, yes, your spouse is cheating.