A term in modern chess that means the beginning position or theoretical starting-point of an opening, the word Tabiya comes from the Arabic tabbiyya, pluralized as tabiyyaat, which translates as "battle array". The word has come to modern times from the old game of Shatranj, which originated in India and spread to Persia where it achieved widespread popularity. Shatranj was a slower game than modern chess, mainly due to the different properties of the pieces: Baidaks, the equivalent of pawns, could only move one square forward on their original move rather than two, and other pieces such as the Fer (queen) and the Alfil (bishop) had reduced mobility compared to their modern chess counterparts. This led to a much greater delay in direct confrontation of the two opposing sides, and the opening strategy pursued by most players was simply to manouever their pieces into a certain prearranged pattern, after which they would begin to calculate tactics for engaging the opponent's pieces. These opening formations, which could be quite varied, were known as tabiyyaat.
In modern chess the word tabiya has come to mean something different from the original Shatranj sense. The definition is somewhat loose, but essentially a tabiya is a position that is reached after a series of practically automatic moves by both players, after which there is a choice of several possible moves or variations depending on a player's taste or their particular analysis. Once two chess masters have determined which opening they are playing, the next few moves until the tabiya is reached will usually be played automatically, at high speed, with neither player calculating at all. This is because the intervening moves have been analyzed to death, with all the possible alternatives experimented with and the consequences known to every competent chess master. Tabiyas can be reached as early as the 5th or 6th move, but in modern chess, and especially since the advent of computer analysis and global databases of chess openings and chess games, tabiyas are often reached surprisingly deep into the game, often the 15th or 20th move, and in some openings even deeper. Also, tabiyas may arise several times during a game, as the following example illustrates.
A simple, early example of a tabiya is the position that arises after the following moves in the Sicilian Defense:
1.e4 c5
2.Nf3 d6
3.d4 cxd4
4.Nxd4 Nf6
5.Nc3
+----+----+----+----+----+----+----+----+
| r | n | b | q | k | b | | r |
+----+----+----+----+----+----+----+----+
| p | p | | | p | p | p | p |
+----+----+----+----+----+----+----+----+
| | | | p | | n | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | N | P | | | |
+----+----+----+----+----+----+----+----+
| | | N | | | | | |
+----+----+----+----+----+----+----+----+
| P | P | P | | | P | P | P |
+----+----+----+----+----+----+----+----+
| R | | B | Q | K | B | | R |
+----+----+----+----+----+----+----+----+
In this position several distinct variations of the Sicilian arise depending on what Black decides to play next. It is the most basic tabiya of the Sicilian, and not even a club-level player would stop to think for long here.
If Black then chooses, for example, the Dragon Variation with 5...g6, the game will typically proceed at a rapid pace for the next 10 or so moves, as both White and Black play moves that they know off by heart, such as:
5...g6
6.Be3 Bg7
7.f3 Nc6
8.Qd2 0-0
9.Bc4 Bd7
10.0-0-0 Rc8
11.Bb3 Ne5
12.h4 Nc4
13.Bxc4 Rxc4
14.h5 Nxh5
15.g4 Nf6
+----+----+----+----+----+----+----+----+
| | | | q | | r | k | |
+----+----+----+----+----+----+----+----+
| p | p | | b | p | p | b | p |
+----+----+----+----+----+----+----+----+
| | | | p | | n | p | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | r | N | P | | P | |
+----+----+----+----+----+----+----+----+
| | | N | | B | P | | |
+----+----+----+----+----+----+----+----+
| P | P | P | Q | | | | |
+----+----+----+----+----+----+----+----+
| | | K | R | | | | R |
+----+----+----+----+----+----+----+----+
Now, on move 15, we've reached another tabiya, except now the decision is up to White. From here he has several moves of varying value from which he can choose, each of which is so complex that no modern grandmaster would think of playing them without deep home preparation, probably computer-assisted. Entire books have been written on single moves played from this point, e.g. 16.Kb1, 16.Bh6, 16.Nde2, 16.Nd5 or 16.Nb3. Each move incorporates a different approach to solving White's problems in this opening, and for any Black player of the Dragon, this tabiya will be so familiar that he will instantly know what his reply to each of these moves will be.
The definition of a tabiya is somewhat imprecise, as mentioned earlier, but the example above leads us to enhance our original definition by saying that for a given position to be a tabiya the chances of both sides must be balanced, and there must be several plausible continuations, with none of the continuations being obviously the best. If there was an obviously best continuation then the position would not be interesting, and the tabiya would arise later, since the function of a tabiya for a chess master is to indicate the best starting-point for his home analysis. Some players would dispute that the position after White's 5th move above is a tabiya, since no master would begin their analysis at that point. Also, some positions that are considered tabiyas for a certain period of time, while grandmaster analysis and practical testing are still ongoing, eventually become played-out and not worth analyzing once the best continuation has finally been established. It will often happen that an extremely popular opening and its associated tabiyas will disappear from top-level praxis because all of the alternatives have been exhausted and there is nothing further of interest to be determined. For a chess position to be a tabiya, it must not be fully understood; it remains alive while it is not understood. Positions that are completely understood are no longer tabiyas; they are dead, and top grandmasters will avoid them.