Is mahjong a single online game or a collection of games?

Answer 1

Mahjong is a traditional Chinese game played using a set of 136 tiles. Games which can be found online are all based off of the original concept of the mahjong solitaire game, and consist of a variety of tile designs and layouts for the player to solve.

Answer 2

Mahjong is a game, played with tiles, that appeared in its current form in the 19th Century in China. It resembles card games of the Rummy family (with which it apparently shares a common, Chinese, much older ancestor), and it has originated simplified modern variants, like the commercial game Rummikub. Like many card games, as Mahjong aged and spread, it developed into somewhat different rulesets, all based on the basic fundamental concept. Think of Poker, and its many varieties and subvarieties. ON THE OTHER HAND, the solitaire tile-matching game, so ubiquitous since the 1990s in computers and as an online pastime, is not--technically--Mahjong. It took that name because it uses a virtual representation of the tile set from the original Mahjong. Alas, its original programmers called it just Mahjong, under which name it became very popular, to the point that most westerners think it is the real game of Mahjong. That it is not! This matching game was never played (and I don't think it is played now) with the physical tiles of the genuine game, as it would be very cumbersome to assemble. It exists only as a software version which uses virtual renderings of said tiles.