A B C D E F G-H I-L M-N O P Q-R S T U-Z

Occupation: Occupation of a file or a rank refers to a Rook or Queen placed in such a way as to exert control over the file or rank. Occupation of a square refers to a piece being safely placed on a square and exerting pressure from it.

Open: Often refers to a type of position (see Open Game) or file (see Open File). This term also refers to a type of tournament in which any class of player can participate. Though a player often ends up with opponents who are much higher (or lower) rated than himself, the prizes are usually structured around classes and, for this reason, are attractive to players of every rating. The open tournament is extremely popular in the United States and is beginning to be seen more and more in Europe.

Open File: A column of eight squares that is free of pawns. It is on open files (and ranks) that Rooks come to their maximum potential.

Open Game: A type of position that is characterized by many open liens and few center pawns. A lead in development becomes very important in positions of this type.

Opening: The beginning phase of a game. This usually encompasses the first dozen moves but it can easily go much further. It is often written that the main opening objectives are: 1) develop your pieces in a quick and efficient manner; 2) occupy as much of the center as possible; 3) castle early (King safety).

While I can say that these objectives are basically correct, the real purpose of the opening is to create an imbalance and develop your pieces in such a way that they all work together in making the imbalance a favorable attribute.

Opposite Color Bishops: Usually called Bishops of opposite colors. A situation in which each player has only one Bishop, each being of a different color, and thus the Bishops can never come into contact. This is usually a good attacking imbalance for the middlegame, since one can°t defend what the other attacks. However, Bishops of opposite color are known as being rather drawish in endgames, due to the fact that the defender can place his pawns and King on the opposite color of the enemy Bishop, whereupon they are impervious to harm.

From an attacking point of view, a general rule for Bishops of opposite colors is that they are at their best with other pieces to back them up. On their own, they are often impotent.

Opposition: An endgame term. The opposition is a means by which one King can dominate another.

Outflanking: An endgame maneuver with Kings which makes forward progress on the board while: 1) simultaneously preventing your opponent from taking direct opposition; or 2) temporarily giving up the opposition for a higher goal.

Overextended: When a player tries to gain some advantages by starting a major advance or offensive, and then this offensive fails, he is often left with various weaknesses and nothing to compensate for them. His position is then said to be overextended.

Overprotection: A term coined by Nimzovich. It refers to defending a strong point more times than appears necessary. The idea is that a certain pawn or square may be causing the opponent (in this case, Black) considerable problems. By focusing so much energy on it, the Black player would be unwise to break that point because that would unleash the latent energy of the White pieces.

Our diagram makes all this clear. White is overprotecting the e5-pawn. The reason he is doing so is that the e5-pawn spearheads a kingside attack by White. Normally Black might wish to close lines there by …f7-f5, but now White would answer this and …f7-f6 with exf6 when all of his pieces have increased their scope and have become extremely active. Thus Black is unable to do anything that would allow White to remove the e5-pawn. As a consequence, his defensive resources are greatly reduced. Also see Prophylaxis.

A B C D E F G-H I-L M-N O P Q-R S T U-Z