A complete reference of Sudoku terminology - from basic concepts like cells and rows to advanced techniques like X-Wing and forcing chains.
As you progress from beginner to advanced Sudoku solving, you will encounter increasingly specialized vocabulary. Understanding these terms is essential for following strategy guides, participating in Sudoku communities, and communicating about puzzles with other solvers.
The terms below are organized alphabetically for easy reference. Basic terms that every solver should know are mixed with advanced strategy terminology. If you are just starting out, focus on learning the fundamental terms first - cell, row, column, box, given, candidate, and house - before exploring the more advanced concepts. For strategy explanations, see our complete strategies guide.
A 3x3 sub-grid within the standard 9x9 Sudoku grid. There are nine boxes in a standard puzzle, and each must contain the digits 1-9 exactly once. Also called a region, square, or nonet.
A digit that could potentially be placed in a given cell based on the current state of the puzzle. As the solver eliminates possibilities, the candidate list for each cell shrinks until only one valid option remains.
A single square in the Sudoku grid that holds exactly one digit when solved. A standard 9x9 grid contains 81 cells. Cells start either filled (as givens) or empty (to be solved).
A sequence of logically connected cells used in advanced solving techniques. Each cell in the chain is linked to the next through shared candidates, allowing the solver to trace implications across the grid.
A vertical line of nine cells running from top to bottom of the grid. Each column must contain the digits 1-9 exactly once. Columns are typically referenced by number from left (1) to right (9).
Two cells in the same house (row, column, or box) that are the only cells containing a specific candidate. If a digit can only go in two places within a house, those two cells form a conjugate pair for that digit.
A rule that limits which digits can be placed in a cell. In standard Sudoku, every cell has three constraints: its row, column, and box must each contain all digits 1-9 without repetition.
A basic solving technique where the solver scans rows and columns passing through a box to determine which cells in that box can contain a specific digit. By eliminating cells already ruled out by existing placements, the solver often finds cells where only one digit is possible.
The fundamental Sudoku solving process of removing impossible candidates from cells. By identifying digits that cannot go in a cell (because they already exist in its row, column, or box), the solver narrows down possibilities.
An advanced technique where the solver assumes a candidate is placed in a cell, then follows the logical consequences through a chain of deductions. If both possible values for a starting cell lead to the same conclusion elsewhere, that conclusion must be true.
A digit pre-filled in the puzzle at the start. Givens are placed by the puzzle designer and cannot be changed. They provide the starting information from which the solver must deduce all remaining digits. A valid puzzle typically has 17-35 givens.
The complete playing field of a Sudoku puzzle. A standard grid is 9 rows by 9 columns (81 cells), divided into nine 3x3 boxes. The grid is the fundamental structure within which all solving takes place.
A solving technique where a candidate appears in only one cell within a house (row, column, or box), even though that cell may have multiple candidates. Since no other cell in that house can hold the digit, it must go in that cell.
A generic term for any group of nine cells that must contain all digits 1-9. In standard Sudoku, there are 27 houses: 9 rows, 9 columns, and 9 boxes. Every cell belongs to exactly three houses.
A situation where a candidate within a box is confined to a single row or column (or vice versa). This allows the solver to eliminate that candidate from other cells in the same row or column outside the box, or from other cells in the box outside that row or column.
Two cells in the same house that contain exactly the same two candidates and no others. Since those two digits must occupy those two cells, they can be eliminated as candidates from all other cells in that house.
Three cells in the same house whose combined candidates include exactly three digits. Those three digits must fill those three cells, so they can be eliminated from all other cells in that house. Each cell may contain two or three of the three candidates.
Four cells in the same house whose combined candidates include exactly four digits. The principle is the same as naked pairs and triples, extended to four cells and four candidates.
A small notation written in a cell to track which candidates remain possible for that cell. Pencil marks are a solving tool, not part of the puzzle rules. They are essential for intermediate and advanced solving techniques.
A specific form of locked candidate where a digit's candidates within a box all fall in a single row or column. The digit can then be eliminated from cells in that row or column outside the box.
Another term for a box or block - a 3x3 sub-grid in standard Sudoku. Some variant puzzles use irregularly shaped regions instead of standard 3x3 boxes. Each region must contain all digits exactly once.
A horizontal line of nine cells running from left to right across the grid. Each row must contain the digits 1-9 exactly once. Rows are typically referenced by number from top (1) to bottom (9).
The simplest category of Sudoku solving techniques. A single occurs when a cell has only one possible candidate (a naked single) or when a digit has only one possible cell within a house (a hidden single).
A cell whose value has been determined, either as a given at the start or by the solver during the solving process. A completed puzzle has all 81 cells solved with no conflicts.
A group of candidates that are confined to an equal number of cells within a house. Naked pairs, triples, and quads are examples of subsets. Hidden subsets work on the same principle from the opposite perspective.
A logic-based number-placement puzzle. The name comes from the Japanese abbreviation of 'Suji wa dokushin ni kagiru,' meaning 'the digits must be single.' The standard format is a 9x9 grid with 3x3 boxes, solved using pure logical deduction.
A Sudoku puzzle where the given digits are arranged in a rotationally symmetric pattern - typically 180-degree rotational symmetry. If you rotate the grid half a turn, the positions of the givens map onto each other. Most published Sudoku puzzles follow this aesthetic convention.
The property that a valid Sudoku puzzle has exactly one solution. Puzzle designers ensure uniqueness during construction. Advanced solvers can sometimes use the assumption of uniqueness to eliminate candidates (uniqueness tests), though this is considered controversial by purists.
An advanced elimination technique. When a candidate appears in exactly two cells in each of two different rows, and those cells share the same two columns, the candidate can be eliminated from all other cells in those two columns (and vice versa for columns and rows).
An advanced technique involving three cells, each containing exactly two candidates. A pivot cell shares one candidate with each of two wing cells. If both wings share a common candidate, that candidate can be eliminated from any cell that sees both wing cells.
Beginner Terms: Cell, Row, Column, Block / Box / Region, Given / Clue, Grid, Sudoku, Pencil Mark, Solved Cell.
Intermediate Terms: Candidate, Elimination, Constraint, House, Crosshatching, Hidden Single, Singles, Locked Candidate, Naked Pair / Triple.
Advanced Terms: Chain, Conjugate Pair, Forcing Chain, Naked Quad, Subset, Pointing Pair, X-Wing, XY-Wing, Uniqueness.
Not at all. Beginners only need to understand basic terms like cell, row, column, box, and given. More advanced terminology becomes useful as you learn intermediate and expert solving strategies. Most casual solvers never need terms like X-Wing or forcing chain.
A naked single is a cell where only one candidate remains after elimination. A hidden single is a candidate that appears in only one cell within a house (row, column, or box), even though that cell may have other candidates. Both result in placing a digit, but hidden singles require scanning the entire house rather than just one cell.
Start with crosshatching, naked singles, and hidden singles. These three techniques can solve most easy and many medium puzzles. Once comfortable, learn locked candidates, naked pairs, and pointing pairs. Advanced techniques like X-Wing and XY-Wing are only needed for the hardest puzzles.
A house is any group of nine cells that must contain all digits 1-9. In standard Sudoku, there are 27 houses: 9 rows, 9 columns, and 9 boxes. The term is used by strategists as a convenient shorthand for 'row, column, or box.'
Each term comes alive when you read it in context. Browse individual entries for box, candidate, cell, crosshatching, elimination, given, house, naked pair, pencil mark, row and column, singles, and X-Wing.
To see the vocabulary applied, read our explainers on Sudoku terminology glossary, Sudoku terminology guide, step-by-step solving, solving strategy summaries, and common Sudoku mistakes. For background, the history of Sudoku, is Sudoku math?, is Sudoku NP-complete?, how Sudoku puzzles are made, can computers solve Sudoku, and how many Sudoku solutions exist articles cover the deeper structure.
Glossary terms also appear across variant Sudoku formats. Try Arrow Sudoku, Greater Than Sudoku, Hyper Sudoku, Jigsaw Sudoku, Sandwich Sudoku, Thermometer Sudoku, or Windoku to see houses, candidates, and pairs in action.
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