Happy to oblige, multiplayer started with games like doom able to handle a whooping 4 players or any game with 2 players on one screen simultaneously if you want to get technical. It went on to 8 on Hexen and games like unreal tournament usually sport between 12 to 32 players per instance/match the term MMO kinda started on E3 on 1995 and was used to describe games handling even more players at the same time and it has since snowballed from there. Going by that, calling a game in 2015 an MMO when its instances cap out at 16 players when we have games like planetside2 having up to 1,000 at the same time use that same description is recklessly misleading if not outright false. By simpler terms any game where you can see big areas crowded by many players at a time could qualify. Detiny's 16 player tower is not an mmo.