SuuudokuuuSudoku Glossary
Updated
Sudoku terms are the grid vocabulary — cell, row, column, box, candidate, given — plus every named solving technique, from full house to alternating inference chain, that justifies a placement or an elimination. This glossary defines all 26 of those techniques plus the core vocabulary, matching the how to play guide and the technique index.
Core vocabulary
- Cell
- One of the 81 positions in the grid, holding either a filled digit or, while blank, a set of candidates.
- Row
- One of the nine horizontal lines of nine cells. Every row must contain the digits 1 to 9 exactly once.
- Column
- One of the nine vertical lines of nine cells. Every column must contain the digits 1 to 9 exactly once.
- Box (unit)
- One of the nine 3×3 blocks of cells. Unit is the general term for any row, column or box.
- Candidate (pencil mark)
- A digit a blank cell could still legally hold, based on what its row, column and box already contain.
- Given (clue)
- A digit printed on the board before solving starts, part of what makes one puzzle different from another.
- Naked patterns are visible in a cell’s own candidates; hidden patterns need checking, unit by unit, for a digit.
- Elimination
- Removing a candidate from a cell because a technique has proven it cannot be the answer, without placing a digit.
- Unique solution
- The property every well-formed Sudoku has: exactly one completed grid satisfies all three rules given its clues.
- Minimal puzzle (17-clue)
- A puzzle with the fewest clues that still has a unique solution — 17 for standard Sudoku.
Solving techniques
Techniques are listed in the difficulty order Suuudokuuu applies them. Every one of them has its own guide with a worked example board built from the real solving engine; the definitions below are the quick-reference version of the same list.
- Full House
- The last empty cell in a row, column or box. It must take the one digit that unit is still missing.
- Naked Single
- A cell whose row, column and box between them eliminate every candidate but one.
- A digit that fits in only one cell of a unit, even though that cell still carries other candidates.
- Pointing Pair
- A digit confined to two cells of a box sharing a row or column, erased from the rest of that line.
- Pointing Triple
- The same pattern as a pointing pair, with three cells confined to a box-line intersection instead of two.
- Box Line Reduction
- The mirror of a pointing pair: a digit confined to one box along a line is erased from the rest of that box.
- Naked Pair
- Two cells sharing the same two candidates and nothing else, so both digits are erased elsewhere in the unit.
- Naked Triple
- Three cells in a unit whose candidates together use only three digits.
- Naked Quad
- Four cells in a unit whose candidates together use only four digits.
- Two digits that fit in only two cells of a unit, which reserves those cells for the pair.
- Three digits confined between them to the same three cells of a unit.
- Four digits confined between them to the same four cells of a unit.
- X-Wing
- A fish pattern: a digit confined to the same two columns across two rows is erased from the rest of those columns.
- Swordfish
- The three-line version of an X-Wing, using three rows and three columns instead of two.
- Jellyfish
- The four-line version of the same fish pattern, using four rows and four columns.
- Finned X-Wing
- An X-Wing with an extra candidate, called a fin, that still supports a smaller set of eliminations near the fin.
- Finned Swordfish
- A Swordfish pattern with fins, the three-line counterpart to a finned X-Wing.
- Sashimi X-Wing
- A finned X-Wing where removing the fin cell’s own candidate entirely still leaves a valid, smaller X-Wing behind.
- Sashimi Swordfish
- The same sashimi pattern applied to a Swordfish instead of an X-Wing.
- XY-Wing
- Three bivalue cells where, whichever value the pivot holds, a shared candidate is erased from cells seeing both others.
- XYZ-Wing
- An XY-Wing where the pivot cell also carries the shared third candidate, which tightens the elimination further.
- W-Wing
- Two cells sharing a candidate pair, linked by a strong link on one digit, that erases the other from shared peers.
- X-Chain
- A chain of strong and weak links on one digit connecting two cells, proving an endpoint of the chain must hold it.
- XY-Chain
- A chain of bivalue cells linked so the two endpoints force an elimination wherever their shared peers overlap.
- Simple Coloring
- Assigns two alternating colors to a chain of strong links on one digit, then clears candidates seeing both colors.
- AIC (Alternating Inference Chain)
- A chain of alternating strong and weak links across candidates, generalising X-Chains, XY-Chains and coloring.
Sudoku glossary FAQ
What is the difference between naked and hidden in sudoku?
Naked patterns show directly in a cell’s own candidates; hidden patterns need checking unit by unit.
Are candidates and pencil marks the same thing?
Yes. Candidate is the term used here; pencil mark is the traditional paper-solving name for it.
What does “unit” mean in sudoku?
Unit is the general term for a row, column or box, the groups that each hold 1 to 9 once.
Ready to put a term into practice? Learn how to play or browse the full technique index.