Does a person have to drink every day in order to be considered an alcoholic?

I have a friend who I suspect is in the beginning stages of alcoholism. He recently drank so much at a baseball game that he fell asleep in his seat and missed half the game. He has also been drunk a few times on a work night recently, at home by himself. He has also told me that he knows it’s time to stop drinking when he begins to dry heave, and that he gets drunk at home way more than he tells me.

However, I also recently went on a week-long cruise with him and his family, and although he did have a few drinks when we were there, he didn’t get drunk once the entire week. I know this because I was basically with him 24/7, since we shared a stateroom and did almost every activity together. So, it’s not like he got drunk at a time we weren’t together. He’d have two or three cocktails a night during the live music shows we went to, and that was it. So, I don’t get it. Was it just because his family was there? There have also been several months in between benders where he stayed sober the whole time, drinking a couple of beers socially.

Anyone care to enlighten me on this?