1. Main line
The principal, most important, or most often played variation of an opening or piece of analysis. For example, 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.0-0 Nc6 8.d5 Ne7 is often referred to as the main line of the King's Indian Defence.
2. Major piece
A queen or rook, also known as a heavy piece.
A larger numbers of pawns on one flank opposed by a smaller number of the opponent's; often a player with a majority on one flank has a minority on the other.
4. Maróczy Bind
A bind on the light squares in the center, particularly d5, obtained by White by placing pawns on c4 and e4. Named for Géza Maróczy, it originally referred to formations arising in some variations of the Sicilian Defence, but the name is now also applied to similar setups in the English Opening and the Queen's Indian Defence. It was once greatly feared by Black but means of countering it have been developed since the 1980s and earlier.
A competition between two individuals or two teams. A match may be the entire competition, or it may be a round in a knockout tournament or team tournament. Unlike in some sports where the word match is sometimes used to describe a single game, a chess match always consists of at least two games (and often many more).
All of a player's pieces and pawns on the board. The player with pieces and pawns of greater value is said to have a "material advantage". When a player gains a material advantage they are also said to be "winning material". (See Chess piece relative value.)
7. Mating attack
An attack aimed at checkmating the enemy king.
Modern Chess Openings, a popular chess opening reference. Often the edition is also given, as in MCO-14, the 14th edition. Cf. ECO.
The part of a chess game that follows the opening and comes before the endgame, beginning after the pieces are developed in the opening. This is usually roughly moves 20 through 40.
A short game (usually no more than 20 to 25 moves), for example 1.e3 e5 2.Qf3 d5 3.Nc3 e4 4.Qf4?? Bd6! and White resigned in NN-Künzel (1900, Europe) because his queen is trapped. However, a significant minority of authors include games up to 30 moves. John Nunn, 101 Brilliant Chess Miniatures, Gambit Publications, 1999, p. 6. ISBN 1-901983-16-1. Usually only decisive games (not draws) are considered miniatures. Ideally, a miniature should not be spoiled by an obvious blunder by the losing side. A miniature may also qualify as a brilliancy. The Opera game is a famous example. Sometimes called a brevity (chiefly British).
11. Minor exchange
The exchange of a bishop for a knight.
12. Minor piece
A bishop or knight.
13. Minority attack
An advance of pawns on the side of the board where one has fewer pawns than the opponent, usually carried out to provoke a weakness.
The ability of a piece, or of a player's pieces collectively, to move around the board. (In computer chess this is often measured by the number of legal moves available.) Effectively means much the same as Space.
15. Mobile pawn center
Pawns on central squares able to advance without becoming weak.
A full move is a turn by both players, White and Black. A turn by either White or Black is a half-move, or one ply.
17. Move order
The sequence of moves one chooses to play an opening or execute a plan. Different move orders often have different advantages and disadvantages. For example, 1.d4 Nf6 2.Nf3 avoids the Budapest Gambit (2.c4 e5!?), but makes it impossible for White to play the Sämisch Variation (2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.f3) or Four Pawns Attack (5.f4) against the King's Indian Defence, and to transpose to certain lines of the Nimzo-Indian Defence and Queen's Gambit Declined, Exchange Variation where the knight goes to e2 instead of f3. (See transposition.)
18. Mysterious rook move
Following Nimzovich's idea, a move with a Rook that seems to have no threat or purpose, but which actually discourages the opponent from a certain type of action (prophylaxis), or sets up a very deep, well-concealed plan.
Symbol used for the knight when recording chess moves in English.
Abbreviation sometimes used for the chess opening reference Nunn's Chess Openings. Cf. ECO and MCO.
21. NN or N.N.
Used in a game score in place of a player whose name is not known. The origin of this usage is uncertain. It may be an abbreviation of the Latin nomina (names), it may be short for the Latin phrase nomen nescio, "name unknown" (literally "I do not know the name") of it may come from the use of "N or NN" (later read as "N or M") in the Anglican Catechism. See also Amateur.
A performance at a chess tournament that indicates a player is ready to receive a title, or the level of performance needed. In addition to other requirements, a certain number of norms is generally required to earn a title. See Grandmaster and International Master.
A new move in the opening. Sometimes called a "theoretical novelty" or "TN."