Glossary

• Naked SingleA state where only one candidate remains for a given cell. The most fundamental solving technique in Sudoku.
• Hidden SingleA state where a specific digit can only be placed in one cell within a row, column, or block.
• Naked PairWhen two cells in the same unit share exactly the same two candidates, those two digits can be eliminated from other cells in that unit.
• Pointing PairWhen all candidates for a digit within a block lie in the same row or column, that digit can be eliminated from other blocks along that row or column.
• X-WingAn advanced technique where a digit's candidates in two rows are confined to the same two columns, allowing elimination from those columns' other cells.
• CandidateThe set of digits that can potentially go in a cell. Recorded as pencil marks, they form the foundation for all solving techniques.
• Given CellA digit pre-placed in the puzzle's initial state. Players cannot modify these cells.
• Unique SolutionThe property of a puzzle having exactly one solution. A mandatory requirement for properly designed Sudoku puzzles.
• BacktrackingA trial-and-error algorithm for finding solutions. When stuck, it reverts to a previous state and tries a different option.
• Box/Line ReductionWhen all candidates for a digit in a row or column fall within the same block, that digit can be eliminated from other cells in that block.
• Hidden PairWhen two digits appear as candidates in only the same two cells within a unit, all other candidates can be removed from those two cells.
• Naked TripleWhen three cells in the same unit have candidates that are subsets of the same three digits, those three digits can be eliminated from other cells in the unit.
• SwordfishAn advanced technique extending X-Wing to 3 rows by 3 columns. Applicable when candidates in 3 rows are confined to at most 3 columns.
• Pencil MarkSmall notations of candidate digits written in a cell. An essential tool for solving intermediate and advanced Sudoku puzzles.
• Constraint PropagationAn algorithmic method that propagates constraints from confirmed digits to related cells, automatically narrowing down candidates.
• Latin SquareA mathematical structure where n symbols are arranged in an n x n grid such that each symbol appears exactly once in every row and column. The foundation of Sudoku.
• Row, Column, and BlockThe three fundamental constraint units in Sudoku. Each unit must contain the digits 1-9 without repetition.
• ChainA family of advanced techniques that trace logical links between candidates to derive contradictions and eliminate possibilities.
• Difficulty RatingA system that classifies puzzle difficulty based on the complexity of techniques required to solve it.
• Daily ChallengeA single puzzle provided each day. All players tackle the same puzzle, promoting habit formation.
• Hidden TripleWhen three digits can only appear in the same three cells within a unit, all other candidates can be removed from those cells.
• XY-WingA three-cell wing structure where shared candidates allow elimination from cells that see both wings.
• ColoringAn advanced technique that traces conjugate pair chains for a digit using two alternating colors to find contradictions.
• Unique RectangleAn advanced technique that exploits the single-solution property to eliminate candidates that would create deadly patterns.
• Box/Line ReductionWhen a digit within a block is confined to one row/column, it can be eliminated from that row/column in other blocks.
• Conjugate PairAn exclusive pair where a specific digit's candidate positions in a row, column, or block are limited to exactly 2 cells.
• Bi-value CellA cell whose candidates are narrowed to exactly 2 digits. Forms the core of advanced techniques like XY-Wing and W-Wing.
• Strong LinkAn exclusive relationship where a digit is limited to exactly 2 cells in a unit, with one of them necessarily true.
• Weak LinkAn exclusive relationship where at least one of 2 cells is not the specific digit, allowing both to be false.
• W-WingAn advanced technique linking two bi-value cells with the same candidates via a strong link to eliminate a specific candidate.
• XYZ-WingA variant of XY-Wing where the pivot has 3 candidates {X, Y, Z} and pincers have 2 candidates {X, Z} and {Y, Z}.
• Flow StateA high-concentration state of immersion in a task that distorts time perception. A concept proposed by psychologist Mihaly Csikszentmihalyi.
• Working MemoryThe cognitive function that temporarily holds and manipulates information. Central to Sudoku solving.
• Mini SudokuSudoku puzzles smaller than the standard 9x9. 4x4 and 6x6 are typical, used for children and beginners.
• Symmetric PuzzleA Sudoku puzzle with mathematical symmetric structure in initial hint placement. Considered a traditional feature of quality puzzles.