Yes
Of couse it is; that's just wrong and cold. Cheating is by definiton having sex with someone who is not your partner.
Cheating
Yes, its that simple if your with some one else at the same time that your in a relationship,your cheating theres no way around it....(friends with benefits) call them what you want cheating is cheating.
Yes you should tell her that he is cheating. Because later, it will hurt her if not told.
Your friend's hot girlfriend. (Ba-dump ching!) I suppose it depends on how good a friend he is, and exactly what you mean by "looking at you."
If you have a girlfriend and a boyfriend, then you are cheating on both of them.
What I would do is tell him that she is cheating and give him some good proof and if he dosent want to believe you then that's his choice. Hey! You warned him!
Friends with benefits is, When you choose to stay friends but you also have exceptions. You will do things that a boyfriend/girlfriend would do like, kiss and other things.
A friend you have sex with but are not dating. Not a boyfriend or girlfriend, just a friend with benefits.
SHOW him that she is cheating. if he knows that you like him, a simple "shes cheating" wont make him understand.
if she is cheating on you if she says she wants to be friends if she broke up with you STUPID!!!!!!! use ur common sense
it depends, if you have a friend with benefits that you makout and ect, yes it is cheating BUT, if you have a frend with benefits but you dont do anything sexual then no its not cheating