Numeric Annotation Glyph (NAG) - Chess Term
Numeric Annotation Glyph (NAG)
Definition
A Numeric Annotation Glyph (often abbreviated as NAG) is a standardized, numeric code used in PGN (Portable Game Notation) to annotate moves and positions. Instead of typographic symbols like !, ?, or ±, NAGs appear as a dollar sign followed by a number (for example, $1, $4, $14). Software then renders these numbers as the familiar glyphs, making annotations machine-readable and language-agnostic.
How It’s Used in Chess
NAGs are placed immediately after the move they annotate in PGN. They encode move quality (good, dubious, blunder), positional evaluations (equal, slight advantage, winning), and sometimes thematic concepts. Because they are numeric, they work reliably across different fonts, locales, and GUIs, and can be parsed by databases, engines, and viewers.
- Placement: 24. Rxd4 $3 indicates “24. Rxd4!!” (a brilliant move).
- Machine-readability: Databases can search/sort for games with $3 (brilliancies) or $4 (blunders).
- Consistency: Different interfaces map the same NAG numbers to the same glyphs, even if fonts/symbols differ.
Common NAGs and Their Meanings
The full list is extensive and comes from the Informant/PGN standards, but the following are widely supported and understood:
- $1 = ! (good move)
- $2 = ? (mistake/poor move)
- $3 = !! (brilliant move)
- $4 = ?? (blunder)
- $5 = !? (interesting move)
- $6 = ?! (dubious move)
- $7 = only/forced move (often shown as a small square ◻ or “only move”)
- $8 = singular move (uniquely best move)
Position-evaluation NAGs commonly used:
- $10 = = (equal position)
- $13 = ∞ (unclear)
- $14 = ⩲ (White is slightly better)
- $15 = ⩱ (Black is slightly better)
- $16 = ± (White has a clear advantage)
- $17 = ∓ (Black has a clear advantage)
- $18 = +− (White is winning/decisive advantage)
- $19 = −+ (Black is winning/decisive advantage)
Note: Different programs may include additional NAGs for concepts like initiative, attack, compensation, zugzwang, etc. Always check your software’s documentation for the full mapping.
Examples
Basic illustration inside a standard opening (Ruy Lopez structure), with annotations described below:
- 11. c4 $5: “!?” — interesting try to grab space on the queenside.
- 12. cxb5 $1: “!” — good capture, undermining Black’s queenside.
- 14. Bg5 $1: “!” — a natural developing move with a tactical eye on e7.
- 14... b4 $6: “?!” — dubious pawn thrust that creates weaknesses.
Famous move example: In Kasparov vs. Topalov, Wijk aan Zee 1999, the spectacular 24. Rxd4 is often annotated 24. Rxd4 $3 (“!!”). You might see a game score like: “... 23... Rf8 24. Rxd4 $3 exd4 25. e5! ...” where $3 highlights the brilliancy.
Strategic and Historical Significance
NAGs originate from the “Informant” system (Šahovski Informator), which codified a rich set of symbols for concise, language-independent annotations in print. When PGN became the standard digital format, numeric codes replaced the printed symbols to ensure portability. This allowed:
- Uniform data exchange: The same annotations render correctly across viewers.
- Searchable analysis: Databases can filter for $4 blunders or $3 brilliancies.
- Engine–human synergy: Engines can auto-tag moves (e.g., $4 for blunders) based on evaluation swings, aiding training and review.
Practical Tips
- Attach the NAG directly to the move token without extra punctuation: 15... c5 $6.
- Use comments in braces alongside NAGs for clarity: 21. Qh5 $5 {Creates kingside pressure}.
- Don’t overuse: Reserve $3 and $4 for genuinely exceptional moments; use $5/$6 to indicate speculative decisions.
- Be consistent: If you use $14/$15 for “slight advantage,” keep the scale coherent throughout a game.
Interesting Facts and Anecdotes
- Many modern GUIs let you annotate with “!” or “??” and convert them to the corresponding NAG automatically when saving to PGN.
- Historic Informant volumes used pictograms (arrows, triangles, etc.); NAGs are their digital heirs, preserving meaning across languages.
- Training workflows often rely on NAGs: blunder-check passes mark $4 positions; repertoire builders search for lines containing $1/$3 moves.
- Because NAGs are numeric, they remain stable even if fonts lack chess-specific symbols like ± or ∞.