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The Lexicon of Sudoku

In the world of Sudoku and solving people tend to use different names for exactly the same thing. This glossary provides a reference for all the different names that people use.

This dictionary includes all the terms found at Sudoku Players Forum

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See: Killer Sudoku

Literally translated means "Sum Number Place".

Keywords: number place

Samurai Sudoku

Five linked sudoku puzzles, where the corner blocks of the five puzzles overlap to form an X shape. Each of the overlapping puzzles shares one block with the central puzzle.

To solve these puzzles, it is recommended that the puzzle be considered as a whole, rather than five separate puzzles.

Also known as: Gattai 5, Kokonotsu, Sudoku-X

Keywords: block, sudoku


The simplest form of Sudoku analysis is practised in two forms.

Cross Hatching
Looking all the positions of a number in the puzzle (for example, all the 1's that you have filled in), you can draw lines through each row the number has been placed in, and each column that the number has been placed in. This will form a series of cross-hatched lines that show where the number cannot be.

If there is only a single cell in a house that has no line running through it, the number must be in that cell. The lines show that there are no other places where that number can be put in that house.

Counting 1-9
Looking at the numbers that appear in a row, column or block is a quick process to work out which numbers are not in that house. By knowing the numbers that are not in that house, it may be possible to identify only one possible position in that hose where a number can be placed.

For example, if a row contains the number 1, 2, 3, 4, 5 and 9, then we know it is missing numbers 6, 7 and 8. Looking at the empty cells in that row, it may be that there is only one cell that can hold the 6 (because there is already a 6 in the same column as one of the three cells, and in the same block as the other one).

Keywords: block, cell, cells, column, house, line, row, single, sudoku


This is a generic term for all of the swordfish derivative methods, x-wing, swordfish, jellyfish, squirmbag, etc.

Also known as: N-Fish

Similar to: Gronk

Keywords: jellyfish, squirmbag, swordfish, x-wing


See: House

This term is used by RubyLips


See: Intersection


See: Nishio

This term is used by Simonis.

Simple Locked Set

See: Number Chains

This term is used by MadOverlord.

Single Numbers

A cell that can only have one possible number in it.

Also known as: Forced, Naked Single, Only Choice

Keywords: cell

Single String Format

A very compact representation of a sudoku grid. Normally a grid can be shown in a grid format:


Most computer solvers can read this format, but it can be easier to represent the puzzle as a single line of text:


This is easier and quicker to input into some solver programs.

Keywords: grid, line, single, sudoku, sudoku grid


A completed puzzle with all the numbers filled in.

Also known as: Completed Grid, Sudoku-Grid

Similar to: Completed Grid, Most Canonical Sudoku Grid


See: Box

Similar to: House


See: Swordfish

This is identical to a swordfish, except you are looking for five conjugates in five rows and five columns, rather than three.

Keywords: column, conjugate, row, swordfish


A stack is a vertical chute.

Also known as: Tower

Keywords: chute

Strangely Familiar

Gordon Royle has collected 29 (although there may be more) sudoku grids that have only 17 clues. What is more, they all have this solution:


Keywords: clues, grid, solution, sudoku, sudoku grid

Strongly Linked

See: Conjugate

This term is used by Simes, Hanson and others.


From the Nikoli website:
"SU" means number, "DOKU" means single.

From the Wikipedia article:

Sudoku, sometimes spelled Su Doku, is a logic-based placement puzzle, also known as Number Place in the United States. The aim of the canonical puzzle is to enter a numeral from 1 through 9 in each cell of a 9x9 grid made up of 3x3 subgrids (called "regions"), starting with various numerals given in some cells (the "givens").

Each row, column and region must contain only one instance of each numeral. Completing the puzzle requires patience and logical ability. Its grid layout is reminiscent of other newspaper puzzles like crosswords and chess problems. Although first published in 1979, Sudoku initially became popular in Japan in 1986 and attained international popularity in 2005.

Also known as: Number Place

Keywords: canonical, cell, cells, column, given, grid, number place, region, row, single, unit

Sudoku Derivations

Suggested derivations of the name Sudoku:

A joke about sudoku or the people addicted to solving them (Neil Campbell)

The state of being a sudoku addict (Neil Campbell)

A person suffering from sudokuitis (Neil Campbell)

A formal fighting sport played between two sudokuicts over sudoku strategy (Neil Campbell)

A well-constructed sudoku puzzle (Roy McCoy)

An attractive woman who does sudoku (Roy McCoy)

As handsome as a very difficult sudoku (Jean Smits)

Popular French variation (Roy McCoy)

The cough remedy of choice for sudokuicts (Gaby Vanhegan)

Pretentious, not a real Sudoku. Also, the act of pretending to be Robert Woodhead. (Max Beran)

Someone who has memorised how many puzzle combinations there are (Max Beran)

The English are renowned for being good at this veriation (Max Beran)

Someone who gains popularity by being good at Sudoku puzzles (Michael Zener Riggs Gottlieb)

To eat while solving puzzles (Jean Smits)

Unskilled sudoku player (Jean Smits)

A player less skilled than a Sudokcoolie (Jean Smits)

That one may take some time to digest (Jean Smits)

A puzzle requiring brainpower (Max Beran)

A puzzle requiring high amounts of brainpower (Max Beran)

A puzzle requiring low amounts of brainpower (Max Beran)

A bread made whilst thinking about Sudoku (Gaby)

A sudokict that's gone over the edge (Mark Hurst)

A competitive game where each player uses really large numbers to push the other players' numbers off the grid (Mark Hurst)

Phil Collins' ode to the game (Mark Hurst)

Sudokats and Sudokitties
Affecting a '50s retro style, these players can be found in coffee shops, identifiable by their sunglasses, black clothes, and really bad poetry (Mark Hurst)

Income derived from a Sudoku-related enterprise (Mark Hurst)

Known as ultimate or Zen Sudoku, this puzzle consists of a 9X9 grid, blank except for the number 1 in the centre (Mark Hurst)

Congratulations for a particularly witty Sudoku joke (Mark Hurst)

Sosumi and Suyutu
Two variants played by lawyers (Mark Hurst)

Global Thermonuclear Sudoku
A strange game. The only way to win is not to play. (Mark Hurst)

Created by, and for cows. (Frank Vedel)

Where you may find animals playing Moodoku. (Frank Vedel)

Someone who practices the art of solving sudokus. Compare to: judoka i.e. someone who practices the art of judo. (Marco Prins)

Found in Haiti over 300 years ago, this ancient form of puzzle curse was bestowed upon outsiders who dared desecrate the sacred lands of the Sood-Oh-Koo.
(Frank Vedel)

Latin for "I play sudoku"
(Frank Vedel)

Keywords: grid, sudoku


See: Solution

Similar to: Completed Grid, Most Canonical Sudoku Grid


See: Samurai Sudoku


An extension of the colouring solving method. Supercolouring looks at the combined consequences of all the colours for all the numbers, and draws conclusions based on the exclusions.

Similar to: Colouring, Multicolouring

Keywords: colouring


A technique that is based on conjugates. If you can find three conjugates of the same number, in three rows, that are in three columns, you can remove that number from the other cells in the conjugate columns.

It works in reverse as well, if you just substitute columns for rows, and vice versa.

Also known as: Jellyfish, Squirmbag, X-Wing

Keywords: cell, cells, column, conjugate, row


See: Digit

A sudoku puzzle does not necessarily have to work with numbers 1 to 9. Any set of 9 different symbols can be used. It could be:

- Letters A to I
- Greek letters
- Chinese characters
- 9 different colours
- Pictures of hamsters
- Any 9, distinctly different symbols

Keywords: sudoku