Sudoku Terms Explained: 21 Words Every Solver Should Know

If you are reading Sudoku guides, watching solve videos, or asking for help in a forum, you will keep running into the same vocabulary. Terms like candidate, house, naked single, and X-Wing make sense once you know them, but they can feel like another puzzle when you are new to the game.

This guide explains the most useful Sudoku terms in plain English. Start with the beginner words first, then move into the strategy terms you will see in harder puzzles.

Sudoku terms at a glance

Here is a quick glossary you can skim before the deeper explanations:

• Grid: The full 9×9 puzzle.
• Cell: One square in the grid.
• Row: A horizontal line of 9 cells.
• Column: A vertical line of 9 cells.
• Box: One 3×3 region.
• House: Any row, column, or box.
• Given: A number printed in the puzzle at the start.
• Candidate: A possible number for a cell.
• Pencil marks: Small notes showing candidates.
• Elimination: Removing an impossible candidate.
• Naked single: A cell with only one candidate left.
• Hidden single: A candidate that appears only once in a house.
• Naked pair: Two cells in one house sharing the same two candidates.
• Hidden pair: Two candidates that can only go in two cells within a house.
• Locked candidate: A candidate restricted to one line inside a box or one box inside a line.
• Pointing pair: A locked candidate pattern from box to row or column.
• Claiming: A locked candidate pattern from row or column to box.
• X-Wing: A rectangle pattern that eliminates candidates across two rows and two columns.
• Swordfish: A larger fish pattern using three rows and three columns.
• Bivalue cell: A cell with exactly two candidates.
• Guessing: Filling a number without proving it through logic.

Core Sudoku terminology every beginner should know

1. Grid

The grid is the entire Sudoku puzzle. In classic Sudoku, it has 81 cells arranged in 9 rows, 9 columns, and 9 boxes.

2. Cell

A cell is one individual square where a number goes. When a guide says “this cell cannot be a 7,” it means one specific square in the grid.

3. Row

A row is a horizontal line of 9 cells. Each row must contain the digits 1 through 9 exactly once.

4. Column

A column is a vertical line of 9 cells. Like rows, columns cannot repeat digits.

5. Box

A box is one 3×3 region. Some guides call it a block. Each box must also contain 1 through 9 exactly once.

6. House

A house is a general term for any row, column, or box. This word matters because many strategy explanations say things like “candidate 4 appears twice in the house.”

7. Given

A given is a number already printed in the puzzle before you start. These starting clues are fixed and cannot be changed.

8. Candidate

A candidate is a number that could still fit in a cell. If a square might be 2, 5, or 8, those three numbers are its candidates.

9. Pencil marks

Pencil marks are the small notes solvers write inside a cell to track candidates. In apps, these are often called notes.

10. Elimination

An elimination happens when logic proves a candidate cannot go in a cell. Good Sudoku solving is mostly a chain of eliminations until only one number remains.

Essential strategy terms in Sudoku

11. Naked single

A naked single happens when one cell has only one possible number left. Example: if a cell can only be 6, you place 6 immediately.

12. Hidden single

A hidden single is different. The cell may still show several pencil marks, but one candidate appears in only one cell within a row, column, or box. That number must go there.

Naked single vs hidden single

This is one of the most common beginner questions. A naked single is obvious because the cell has one candidate. A hidden single is hidden because the house has one valid place for that candidate.

13. Naked pair

If two cells in the same house share the exact same two candidates, those numbers must belong in those two cells. That means you can remove those candidates from the rest of the house.

14. Hidden pair

A hidden pair appears when two candidates can go in only two cells of a house, even if those cells currently show other notes. You can keep the pair and erase the extra candidates from those two cells.

15. Locked candidate

A locked candidate means a number is confined in a way that creates eliminations elsewhere. This term includes two important subtypes: pointing and claiming.

16. Pointing pair or pointing triple

If all possible positions for a number inside one box fall in the same row or column, that candidate can be removed from the rest of that row or column outside the box.

17. Claiming pair or claiming triple

If all possible positions for a number in one row or column are inside the same box, that candidate can be removed from the other cells in that box.

18. Bivalue cell

A bivalue cell has exactly two candidates. These cells are especially important in advanced techniques such as XY-Wing.

Advanced Sudoku terms you will see in hard puzzles

19. X-Wing

An X-Wing is a pattern where one candidate appears in exactly two positions in each of two rows, and those positions line up in the same two columns. That creates eliminations in the columns. The same logic can work row-wise or column-wise.

20. Swordfish

A Swordfish is an extension of the X-Wing idea across three rows and three columns. It is less common, but it appears in harder puzzles and expert-level strategy guides.

21. Guessing

Guessing means placing a number before logic proves it. Some solvers use controlled trial and error, but most classic strategy guides treat guessing as something to avoid until you have exhausted clean logical moves.

How Sudoku notation works in guides and forums

When people discuss Sudoku online, they often use coordinates like r3c7. That means row 3, column 7. Once you know this notation, forum explanations become much easier to follow.

Example: “r3c7 = 4” means the cell in row 3, column 7 is 4. “Remove 8 from r5c2” means 8 is not a valid candidate in row 5, column 2.

Why learning Sudoku terms helps you solve faster

• You can understand tutorials without stopping every sentence.
• You will recognize patterns like hidden singles and pointing pairs faster.
• You can ask better questions when you get stuck.
• You can move from beginner guides into advanced strategy articles more smoothly.

FAQ: Sudoku terms explained

What is the most important Sudoku term for beginners?

Candidate is the most important term because almost every strategy depends on knowing which numbers are still possible in each cell.

What is the difference between a box and a house in Sudoku?

A box is one 3×3 region. A house is a broader term that means any row, column, or box.

What does r1c1 mean in Sudoku?

It means row 1, column 1. This coordinate system is standard in Sudoku explanations, solver tools, and online communities.

Is a hidden single harder than a naked single?

Usually yes. A naked single is visible in one cell. A hidden single requires scanning the whole row, column, or box to see that only one cell can take that number.

Conclusion

Once these Sudoku terms become familiar, strategy guides stop sounding technical and start feeling practical. Learn the beginner vocabulary first, especially candidate, house, naked single, and hidden single. Then build toward patterns like pointing pairs, X-Wing, and Swordfish.

If you want to put these terms into action, play a fresh puzzle and focus on naming each move as you make it. That habit makes every solving session more deliberate and helps the patterns stick.