As with checkmate, stalemate has passed into common parlance as a word indicating a deadlock between two opposing sides, perhaps where neither side is willing to compromise, or where neither side is capable of winning the conflict. Unlike checkmate, which is derived from the Persian for The king is dead, stalemate entered the language in roughly 1765, with the 'mate' part taken from checkmate and 'stale' possibly coming from the Anglo-French estale, or "standstill".
In chess, stalemate occurs when the player to move has no legal move available, and is not in check. If stalemate occurs, the game is declared a draw. The simplest possible stalemate, and one of the most common, occurs in the endgame King and Pawn vs. King, in which the Black king is trapped on the back rank behind the White king and pawn:
+----+----+----+----+----+----+----+----+
| | | | | k | | | |
+----+----+----+----+----+----+----+----+
| | | | | P | | | |
+----+----+----+----+----+----+----+----+
| | | | | K | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
Note that the interpretation of this position depends entirely on which player is to move. If it is White to move, then 1.Kd6 forces the Black king to move to f7, after which 2.Kd7 wins, forcing the promotion of the pawn to queen on e8 next move, with a quick checkmate to follow. However, with Black to move, the game is a draw, since the Black king is not in check but has no legal moves (all the available squares are attacked by either the White pawn or king, which would involve Black moving into check, which is illegal. Therefore, because there are no legal moves, it is stalemate.<;/p>
Understanding of the above position is essential to the play of endgames, and is covered in detail in The Opposition, King vs King and single pawn. However, stalemate can also occur in more complicated positions. An example:
+----+----+----+----+----+----+----+----+
| | | | | | | k | |
+----+----+----+----+----+----+----+----+
| | | | | | | r | p |
+----+----+----+----+----+----+----+----+
| | | | | | | p | |
+----+----+----+----+----+----+----+----+
| | p | B | | | p | P | |
+----+----+----+----+----+----+----+----+
| p | P | | | | P | N | |
+----+----+----+----+----+----+----+----+
| P | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | P |
+----+----+----+----+----+----+----+----+
| | | | | | | K | |
+----+----+----+----+----+----+----+----+
Here White has the advantage in the endgame - the bishop and knight are worth slightly more than Black's rook, but it will take a long time to win. White thinks he sees a faster win, and plays: 1.Nh6+ (1.Ne5 is better). Black plays 1.Kh8, the only legal move as the f7 square is covered by the knight and f8 by the bishop. White follows with 2.Bd4, only to realize that the position is stalemate - Black's king is locked into the corner, with its only escape square covered by the knight on h6; the rook on g7 is pinned by the bishop, and cannot move without placing Black in check; and all Black's pawns are blockaded by White pawns or pieces.
+----+----+----+----+----+----+----+----+
| | | | | | | | k |
+----+----+----+----+----+----+----+----+
| | | | | | | r | p |
+----+----+----+----+----+----+----+----+
| | | | | | | p | N |
+----+----+----+----+----+----+----+----+
| | p | | | | p | P | |
+----+----+----+----+----+----+----+----+
| p | P | | B | | P | | |
+----+----+----+----+----+----+----+----+
| P | | | | | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | P |
+----+----+----+----+----+----+----+----+
| | | | | | | K | |
+----+----+----+----+----+----+----+----+
Etymology:
http://www.geocities.com/etymonline/s5etym.htm