*A chat room would not be a virtual world because it has no physics; a strategic wargame doesnt map the player onto a single character through which that player acts; a play-by-email game doesnt run in real time; a single-player game is not shared; a first-person shooter isnt persistent.
For some examples, the case is not so clear-cut. Are tabletop role-playing games virtual worlds, for example? No, because they are not automated, but it is a close call. Would a two-player educational MUD be a virtual world? Probably. Would a 500-player game with a world so vast that the players could never find each other? Yes, but under protest.
In practice, its fairly easy to determine what is or isnt a virtual world simply by looking at its heritage. If its design draws heavily from the design of an existing virtual world, it almost certainly is one; if it doesnt, it almost certainly isnt.

Ahoj. Este to potrebujes?