Sudoku Terminology: A Clear Guide to the Words Every Solver Should Know
If you have ever read a strategy guide and wondered what words like candidate, given, naked single, or X-Wing actually mean, this Sudoku terminology guide is for you. Learning the language of Sudoku makes it easier to follow tutorials, spot patterns faster, and talk about puzzles without confusion.
In simple terms, Sudoku terminology is the shared vocabulary solvers use to describe the grid, the starting clues, pencil marks, and the solving techniques that unlock tougher puzzles.
Some terms have more than one accepted name. For example, a box may also be called a block or region. That is normal. What matters is understanding the idea behind the word.
Quick Sudoku Terms Reference
| Term | What It Means |
|---|---|
| Grid | The full 9×9 Sudoku board. |
| Cell | One square in the grid. |
| Row | A horizontal line of 9 cells. |
| Column | A vertical line of 9 cells. |
| Box / Block / Region | One 3×3 section of the grid. |
| Given / Clue | A number that is already placed at the start. |
| Candidate | A possible number for an empty cell. |
| Pencil Marks / Notes | Small candidate numbers written in empty cells. |
| Peer | A cell that shares a row, column, or box with another cell. |
| Naked Single | A cell with only one possible candidate left. |
| Hidden Single | A number that appears only once in one row, column, or box. |
| Naked Pair | Two cells in one unit that share the same two candidates. |
| Locked Candidates | A candidate restricted to one line inside a box, allowing eliminations. |
| X-Wing | An advanced rectangle pattern used to remove candidates. |
| XY-Wing | An advanced three-cell pattern based on linked bivalue cells. |
Basic Grid Terms in Sudoku Terminology
Grid
The grid is the entire Sudoku puzzle: 9 rows, 9 columns, and 81 cells total.
Cell
A cell is a single square where one digit must eventually go.
Row and Column
A row runs left to right. A column runs top to bottom. Every row and every column must contain the digits 1 through 9 exactly once.
Box, Block, or Region
These three words usually mean the same thing: one of the nine 3×3 sections in a classic Sudoku grid. Different guides prefer different terms, so it helps to recognize all three.
Unit or House
A unit or house means any row, column, or box. When a guide says “check the unit,” it means check one of those three structures.
Band and Stack
These are less common beginner terms, but you may still see them in advanced discussions. A band is a horizontal set of three boxes. A stack is a vertical set of three boxes.
Setup Terms Every Solver Should Know
Given or Clue
A given, also called a clue, is a number that appears in the puzzle before you start solving. You do not change givens.
Candidate
A candidate is a number that could legally go in an empty cell based on the current state of the puzzle.
Example: if a cell cannot be 1, 2, 3, 4, 5, 7, or 9, then its remaining candidates might be 6 and 8.
Pencil Marks or Notes
Pencil marks are the small candidate numbers you write in empty cells. Good note hygiene matters. Old, incorrect notes hide simple moves and create unnecessary mistakes.
Bivalue Cell
A bivalue cell is a cell with exactly two candidates left. These cells matter because many advanced patterns, including XY-Wing, start from them.
Peer
Two cells are peers if they share a row, column, or box. Because peers cannot contain the same digit, peer relationships drive most eliminations in Sudoku.
Common Solving Terms in Sudoku Terminology
Scan or Scanning
Scanning means moving through the grid deliberately to look for missing digits, weak spots, or obvious eliminations. Strong solvers do not stare randomly; they scan with a plan.
Crosshatching
Crosshatching is a beginner-friendly technique where you track one digit at a time across rows and columns to see where it can still fit inside a box.
Elimination
An elimination removes a candidate from one or more cells because logic proves that candidate cannot go there.
Naked Single
A naked single happens when one cell has only one candidate left. If a cell can only be 4, you place 4 immediately.
Hidden Single
A hidden single happens when a digit appears as a candidate in only one cell of a row, column, or box. The cell may still show several notes, but only one of them works in that unit.
Naked Pair, Triple, and Quad
If two cells in one unit share the same two candidates, those digits must stay there, so you can remove them from the rest of the unit. The same idea extends to triples and quads.
Hidden Pair, Triple, and Quad
This is the reverse idea. If two digits can only appear in the same two cells of a unit, those cells must contain those digits, even if other notes are still written there. You can then erase the extra candidates.
Locked Candidates
Locked candidates are candidates trapped in a single line inside a box or trapped in a single box along a line. This leads to eliminations outside the immediate area.
You may also see the related names pointing and claiming:
- Pointing: a candidate is confined to one row or column inside a box, so it can be removed from the rest of that row or column outside the box.
- Claiming: a candidate is confined to one box within a row or column, so it can be removed from the rest of that box.
Advanced Pattern Terms You Will See in Harder Puzzles
X-Wing
An X-Wing is a four-cell rectangle pattern built on one digit. When that digit appears in exactly two positions across two rows and the columns line up, or vice versa, you can eliminate that digit from other cells in the matching columns or rows.
Swordfish
Swordfish is similar to X-Wing but uses three rows and three columns instead of two. It is harder to spot, but the logic is the same: a candidate is restricted to a structure that lets you clear it elsewhere.
XY-Wing
An XY-Wing uses three bivalue cells: one pivot and two wings. When the structure is valid, a shared candidate can be removed from cells that see both wings.
Coloring
Coloring is a chain-based technique that marks alternating possibilities for one candidate. If one color creates a contradiction, the opposite color must be true.
Chain
A chain is a linked sequence of logical relationships. You will see this term often in advanced Sudoku discussions, especially around coloring, forcing chains, and wing patterns.
Difficulty and Puzzle-Type Terms
Easy, Medium, Hard, and Expert
These labels usually describe the solving techniques required, not the number of givens. An easy puzzle may be solvable with singles and simple pairs. A hard or expert puzzle often requires advanced eliminations such as X-Wing, Swordfish, or chain-based logic.
Classic Sudoku
This is the standard 9×9 puzzle with rows, columns, and 3×3 boxes.
Variant Sudoku
Variant Sudoku adds extra rules. Common examples include:
- Killer Sudoku: cages must add to a target sum.
- Jigsaw Sudoku: boxes become irregular regions.
- Diagonal Sudoku: both main diagonals must also contain 1 through 9.
- Samurai Sudoku: multiple overlapping grids form one large puzzle.
Why Learning Sudoku Terms Helps You Solve Better
Knowing Sudoku terminology is not just about sounding technical. It gives you practical advantages:
- You can follow tutorials faster because you understand the language immediately.
- You can explain why a move works instead of guessing.
- You can study advanced guides one concept at a time.
- You can review your own mistakes with more precision.
If you want to turn vocabulary into results, study our Sudoku solving strategies guide, practice with printable Sudoku blank grids, or build consistency with the daily Sudoku puzzle.
Frequently Asked Questions
What is the most important Sudoku term for beginners?
Start with row, column, box, candidate, given, naked single, and hidden single. Those terms cover the moves beginners use most often.
What is the difference between a given and a candidate?
A given is a number printed in the puzzle at the start. A candidate is a possible number for an empty cell while you solve.
Are box, block, and region the same in Sudoku?
Usually yes. Most guides use those words interchangeably for the 3×3 sections of a classic Sudoku grid.
Do I need to know advanced Sudoku terminology to solve easy puzzles?
No. Easy puzzles usually rely on scanning, crosshatching, and singles. But knowing advanced terms helps when you move up in difficulty or read strategy content online.
Conclusion
Sudoku gets easier to learn when the language stops feeling mysterious. Once you understand terms like candidate, peer, naked single, and locked candidates, strategy guides become much more useful and advanced techniques feel less intimidating.
Use this Sudoku terminology guide as a reference, then put the terms into practice on a fresh puzzle. The fastest way to remember the vocabulary is to apply it while you solve.