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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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Each of the outlined areas in a killer sudoku is referred to as a cage. Each cage has a number in it, which is the sum of all the numbers that appear in that cage.

Some variations use the product of the numbers in the cage.

Keywords: killer sudoku, line, sudoku

Candidate List

See: Candidate Numbers

The list of possible numbers that could go into a cell

Similar to: Candidate Numbers

Keywords: cell

Candidate Numbers

The list of possible numbers that could be put into a cell.

Also known as: Candidate List, Candidates, Pencilmarks

Similar to: Candidate List, Pencilmarks

Keywords: cell

Candidate Removal

See: Eliminate

This is a broader description of any of the advanced techniques that can help in eliminating numbers from a cell.

Keywords: cell


See: Candidate Numbers

Similar to: Pencilmarks

Canonical Form

A sudoku is in it's most canonical form when it has been completely filled in, and there are no empty cells.

Keywords: cell, cells, sudoku


An individual square in a puzzle that you put a number in.

Also known as: Cells, Line

Keywords: square


See: House

This term is used by Gaby


A line of three blocks, either horizontal or vertical.

This term is used by Dukuso.

Keywords: block, line


The numbers that are already in the grid when you begin.

Also known as: Givens, Initial Numbers

Keywords: grid


A technique that involves colouring conjugate cells with different colours, and using the colouring scheme to work out if combinations of numbers are invalid.

Also known as: X-Cycles

Similar to: Multicolouring, Supercolouring

Keywords: cell, cells, conjugate


A column of 9 cells that runs the height of the board.

Similar to: Line

Keywords: cell, cells

Completed Grid

See: Solution

Similar to: Solution, Sudoku-Grid

Comprehensive Locked Set

See: Number Chains

This term is used by MadOverlord

Similar to: Number Chains, Number Pairs


This term is used by Eppstein and is one of his five solving techniques:

Look for conflicting paths of bilocated or bivalued cells. In the same graph used by the bilocal and repeat rules, if there exist two paths that start with the same cell and digit, and that end with equal digits in different cells of the same row, column, or square, then the start cell must contain the starting digit for otherwise it would cause the end cells to conflict with each other. One or both paths can instead be in the bivalue graph, starting and ending with the other digit than the one for the bilocal path. We also find similar pairs of paths that end in sets of cells that together eliminate all positions for the end digit in another row, column, or square of the grid.

Keywords: bilocal, bivalue, cell, cells, column, digit, eliminate, eppstein, grid, path, repeat, row, square, value


Conjugates are a pair of cells in a row, column or block which are the only two places in that row, column or block where a given number can go. For example, if you look along a row at the candidate numbers, and you find that the number 2 can only appear in two cells on that row, then those two cells form a conjugate pair.

Conjugates are used extensively in techniques like swordfish, fishy cycles, colouring, and other logic techniques.

Also known as: Conjugate Pair, Remote Locked Pair, Strongly Linked, Vertex Groups

Similar to: Bilocal

Keywords: block, candidate, cell, cells, colouring, column, conjugate pair, fishy cycles, given, row, swordfish

Conjugate Pair

See: Conjugate

This term is used by AMcK.

Similar to: Bilocal


Rules, or conditions that must be met.


The factors that limit the placement of a number. For example, already having a number in a row or column may affect where that number could be placed in a block.

For example, it may only be possible to place number X in cell A if cell B is given number Y.

Keywords: block, cell, column, given, row