How to use this glossary
Sudoku picked up a vocabulary of its own as solvers named the patterns they kept meeting. Most of the words are simple once someone defines them plainly, but puzzle books and apps tend to use them without explanation. This page collects the terms you will run into in Sudoku by WizusLabs and in almost any guide, grouped from the parts of the board up to the advanced patterns. Read it straight through once, or keep it open in a tab while you solve.
The board
Grid. The whole playing area. A classic sudoku grid is nine cells wide and nine cells tall, eighty-one cells in total. Variants change the size — a Mini grid is six by six, a 12×12 grid is twelve by twelve.
Cell. A single square in the grid, the smallest unit you can write a digit into. Each cell holds exactly one digit in a finished puzzle.
Row. A horizontal line of cells that runs the full width of the grid. In classic sudoku each row must contain every digit from 1 to 9 exactly once.
Column. A vertical line of cells that runs the full height of the grid. Like a row, each column must contain every digit exactly once.
Box, block, or region. A smaller bordered group of cells — three by three in classic sudoku — that must also contain every digit exactly once. "Box" and "region" are used interchangeably; irregular variants call the same idea a jigsaw region.
Unit or house. A general word for any group that must hold each digit once — that is, any row, column, or box. Solving techniques are usually described in terms of units so they apply to all three at once.
Given or clue. A digit the puzzle supplies at the start, printed and locked so you cannot change it. The number and placement of givens is what sets a puzzle's difficulty.
Peer. Any cell that shares a row, column, or box with a given cell. A cell's peers are exactly the cells whose contents constrain it, so a digit placed in one cell is forbidden in all of its peers.
Candidates and notes
Candidate. A digit that could still legally go in a particular empty cell given what has been placed so far. Solving is largely the work of eliminating candidates until one remains.
Pencil mark. A small candidate digit noted in the corner of a cell to track the possibilities. In Sudoku by WizusLabs these notes are built in, so you can mark up a cell without keeping a mental ledger.
Elimination. Removing a candidate from a cell because a rule or pattern rules it out. Every solving technique is, at heart, a justified elimination.
Single-cell deductions
Naked single. A cell that has only one candidate left, so that digit must go there. Naked singles are the most direct move in sudoku and often cascade once you place the first one.
Hidden single. A digit that can legally go in only one cell of a given row, column, or box, even though that cell may still show several candidates. The digit is "hidden" among other candidates but is forced by being unplaceable anywhere else in the unit.
Pairs, triples, and locked candidates
Naked pair. Two cells in the same unit that between them hold only the same two candidates. Those two digits are locked to those two cells, so both can be eliminated from every other cell in the unit.
Hidden pair. Two digits that appear as candidates in only two cells of a unit, even if those cells also carry other candidates. Once found, every other candidate can be cleared from those two cells, revealing the pair.
Naked triple. Three cells in a unit whose candidates together use only three digits. As with a naked pair, those three digits can be removed from the rest of the unit. Each cell need not show all three digits — just no digit outside the set of three.
Hidden triple. Three digits confined to the same three cells of a unit, hidden among other candidates. Clearing the extra candidates from those three cells exposes the triple.
Pointing pair. When a digit's only candidates within a box all sit in the same row or column, that digit must fall somewhere in that line inside the box — so it can be eliminated from the rest of the row or column outside the box. The candidates "point" out of the box along the line.
Box-line reduction. The mirror of the pointing pair. When a digit's only candidates within a row or column all sit in one box, that digit must be inside that box on that line, so it can be eliminated from the rest of the box.
Advanced patterns
X-Wing. A pattern across two rows and two columns. When a digit's candidates in two rows are confined to the same two columns, that digit can be eliminated from those two columns everywhere else — and the pattern works with rows and columns swapped.
Swordfish. The three-line extension of the X-Wing. A digit whose candidates across three rows occupy only three shared columns can be eliminated from those columns elsewhere. Larger versions with four lines are called jellyfish.
Unique rectangle. A safeguard pattern that exploits the fact that a well-formed sudoku has exactly one solution. If four cells forming a rectangle across two boxes would all reduce to the same two candidates, the puzzle would have two solutions, so at least one of those cells must take a different digit — which lets you eliminate the deadly repeat.
Guessing versus deduction. A well-formed puzzle can always be finished by deduction alone, without guessing. Every puzzle in Sudoku by WizusLabs has exactly one solution, so the patterns above will always resolve it logically.
Killer sudoku terms
Cage. A dotted outline grouping cells in killer sudoku, carrying a target sum in its top-left corner. The digits inside a cage must add up to that sum, and no digit may repeat within the cage.
Cage combination. The set of distinct digits that can fill a cage of a given size and sum. Small cages often have only one combination — a two-cell cage summing to 17 can only be {8, 9} — which makes them powerful starting points.
Rule of 45. Because each row, column, and box holds the digits 1 to 9, every one of them sums to 45. In killer sudoku you subtract the known cage sums in a region from 45 to find the value of a leftover cell.
Innie and outie. A single cell that a cage pokes into a region from outside (an innie) or carries just beyond a region's edge (an outie). Comparing cage sums to 45 pins down these stray cells. The full method lives in the killer sudoku rules and strategy guide.
Keep going
Sudoku by WizusLabs generates every puzzle on device, works offline with progress saved locally, and gives each puzzle exactly one solution — so every term above earns its keep at the board.
Keep reading: classic vs killer sudoku · sudoku variants explained · all guides