When A Guy Says Hi To You Are They Interested In You?

Well it exactly doesn't mean that he's interested in you. But still this can be a sign for the start of a relation. When you really like someone you would definitely want to know that person's inside out. What they like eating, where they like going? What they like doing when they are free? What makes them smile? What makes them feel sad?? Maybe that person is trying to get to know you. Just saying hi is not the signal though but still you can take it as a positive sign. But you shouldn't get yourself all carried away. This seriously means just a simple hi. Just try and see his moves and his behavior towards you. But you should be ready for any kind of a comment.
Maybe its possible he's seriously trying to know you, will in that case, don't let him know that you know what's on his mind. This is mainly because guys like to play around with stuff which is difficult to solve. So try and be like a puzzle, let him try and figure you out. Don't give up that soon. And you'll see the results. Be his friend and try and know him properly but never let him know that you know what he's up to. So best of luck with the new mission!!!!

Not usually.  But if they say hi and then start flirting with you, they might like you.  If they flirt, flirt back.  They'll probably ask you to hang out, and then maybe it will turn into something more.  Just hope for the best. :D

This guy say bye to me and then he get close to me and just looked at me then he say bye again but I didnt answer him because I don't know him but he knows me.

It is hard to say. It could be that he was just being cordial. Do you see him all the time, has he asked your name, has he struck up conversations with you? Have you noticed whether or not he watches you?
Usually when a guy just says hi, then it is something said in passing, a greeting. Don't get over excited over this, don't want you to get your hopes up too high. Strike up a conversation with him next time you see him, maybe then you will have a better idea of whether he likes you. Good luck.

I don't think so, not necessarily they are interested.

Well if you don't know him and he is seeing you in the hall or what ever saying hi then that means that he would like you but, if he knows you and is saying hi that necessarily does not mean that he likes you.

There is a boy who is on my bus and yesterday he saw me in the hall and he said  hi but  I didnt see him. And I kinda like him