ChessWorld Glossary

ChessWorld Hitchhiker's Guide to Chess

Scope: This glossary does not intend to cover player names, opening names, or Composition terms. The Glossary aims to relate the terms to ChessWorld where possible when giving examples.
If you have contributions, corrections or questions, please post them to the Chess Forum for discussion.
There is a dedicated Chess Openings Glossary

Glossary Course Modules with Game Examples

Glossary Course Modules with Tactical Puzzle Examples

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I

Illegal move
A move which is not permitted by the laws of chess governing the movement of the pieces. If an illegal move is discovered during the course of an Over-the-board game, the position must be reset to the point of the illegal move, and play resumed from there. If it is not discovered, and the game is decided, then nothing can be done about it.

The basic rules which govern piece movement are:-

Rooks only move across the ranks or files
Knights move in an L shape
Bishops move across the diagonals on the same colour they started on
Kings move in any direction but one square at a time only
Queens move in any direction any number of squares

More subtle rules include castling rules, enpassant rules, etc.

Chessworld automatically enforces legal moves only and will prevent a player from playing an illegal move.

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Imbalance
IM Jeremy Silman defines the term "Imbalance" as :

Any difference between the White and Black positions. Material advantage, superior pawn structure, superior minor piece, space, development and the initiative are all typical imbalances.

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Initiative
The player with the "initiative" is the player who is able to make more threats than the opponent and often this means keeping the opponent on the defensive. White who has the 1st move has the initiative by default, and black often has to try and equalise.

In the Romantic era of chess, players used very aggressive gambit systems to maximise the power of the intiative, and often because defensive technique was quite poor, the result was a large number of brilliant attacking games resulting in spectacular victories for the attacker. The battle for the initiative can occur at any stage of the game particularly in the middlegame where players will often sacrifice material for initiative. Some players like to snap up the material and don't mind playing defensively for long periods of time if they think they can eventually beat off the attack and the initiative and win in the long term. In closed positions, the battle for the initiative is often less relevant because Time and Tempo is not such an important factor in the position.

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Interference
Two meanings include:-

1) When an outside observer interferes with a game in progress. Such interference is not generally permitted. It is also not permissible in an over-the-board game for a spectator to indicate if one side's clock has fallen. This would constitute interference.

2) Interference is also a tactical motif. It is a move which obstructs the line of attack or defence of enemy pieces.

An example is shown below from the game Hartston vs Westerinen:

Analyse position

Westerinen plays the move Nd3+ which "interferes" with the protection of the d4 knight in a spectacular way.

Analyse position

Here is the game score:-

[Event "Havana ol (Men) fin-B"]
[Site "Havana"]
[Date "1966.10.25"]
[Round "11"]
[White "Hartston,William R"]
[Black "Westerinen,Heikki MJ"]
[Result "0-1"]
[Eco "B79"]

1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 g6 5.Be3 Bg7 6.Nc3 Nf6 7.Bc4 0-0 8.Bb3 d6 9.f3 Bd7 10.Qd2 Qa5 11.h4 Rfc8 12.h5 Nxh5 13.0-0-0 Ne5 14.Bh6 Nd3+ 15.Qxd3 Bxh6+ 16.Kb1 Rxc3 17.Qxc3 Qxc3 18.bxc3 Bg7 19.Rhe1 a5 20.a4 Rc8 21.Kb2 Nf4 22.g3 Ne6 23.Re3 Nc5 24.Ka3 Bh6 25.f4 e5 26.Ne2 Bc6 27.Bd5 Bxa4 28.Rf3 Bxc2 29.Rh1 Bf8 30.fxe5 Bxe4 31.Bxe4 Nxe4 32.exd6 Bxd6+ 33.Ka4 Rc4+ 34.Kb5 Rc5+ 35.Kb6 Bc7+ 36.Kxb7 Nd6+ 37.Ka8 a4 0-1

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International Arbiter
A referee at International chess events.

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International Master
An internationally recognised chess expert. This title is immediately below that of Grandmaster.

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Isolated pawn
A pawn is said to be isolated when there are no pawns of the same colour on adjacent files. For example the d6 pawn in the diagram below is "isolated" :

Analyse position

Generally isolated pawns are considered to be weak but players such as Tarrasch believed that isolated pawns could be compensated by mobility.

Tarrasch forged the Tarrasch defence as a major weapon to 1.d4 which features an isolated Queen pawn. Black often gets sufficient counterplay to balance this structural weakness. There is also the Tarrasch variation of the French defence where French defence exponents willingly accept an isolated Queen pawn in return for some dynamic piece activity.

The Isolated *Queen* pawn in particular provides support for central outposts and can be a strenght as well as a weakness. The following Karpov game video shows how Karpov manoevered against Huebner's isolated pawns, and also temporarily accepted isolated pawns himself, which he eventually mended:

Methods of isolating opponents pawns include:

1) Sacrifing a pawn: Sometimes one can sacrifice a pawn to create isolated pawns in the opponent's position - and when the material is regained, then those isolated pawns can become under fire.

2) "Minority attack" : With a minority attack, the end result can often be an isolated d pawn in the opponents position.

Attacking with an isolated pawn

In the following video annotated game, Kasparov had black with the isolated pawn, but managed to get a very good attack and compensation despite this structural weakness. The isolated pawn supported key outpost squares and supported the attack:

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