A classic Sudoku grid looks simple: 81 cells in a 9×9 square. The important part is that the same cells are organized in three overlapping ways — rows, columns, and 3×3 boxes.
Every solving rule depends on those overlaps. Once you can look at one cell and immediately see its row, column, box, and peers, later concepts such as candidates, Locked Candidates, and Chains become much easier to follow.
Cells
A cell is one square in the Sudoku grid.
A cell can be:
- a given, supplied by the puzzle
- an unsolved empty cell
- a cell solved by the player
When candidates are enabled, an unsolved cell can also display small candidate digits.
Rows
A row is a horizontal group of nine cells.
There are nine rows in classic Sudoku. In a completed puzzle, every row contains the digits 1–9 exactly once.
Rows are commonly numbered 1–9 in coordinate notation.
Columns
A column is a vertical group of nine cells.
There are nine columns, and every completed column also contains 1–9 exactly once.
Columns are numbered 1–9 in VeyraPlay's technical coordinate notation.
Boxes
A box is one of the nine 3×3 areas separated visually by stronger grid lines.
Each box contains nine cells and, when solved, the digits 1–9 exactly once.
Other Sudoku resources may call these areas blocks or regions. VeyraPlay uses box as its default term for classic Sudoku.
Units
A unit is a useful collective term for a row, column, or box.
Instead of writing:
this works in any row, column, or box
an intermediate or advanced explanation can say:
this works in any unit
Beginner Guides should still spell out the three structures when clarity matters.
Peers
Two cells are peers when they share a row, column, or box.
If r4c7 contains a solved 8, every unsolved peer of r4c7 can eliminate 8 from its candidates.
Peers are especially useful when describing candidate updates and advanced solving logic.
Givens and clues
A given is a digit supplied in the starting puzzle. The word clue is also common.
VeyraPlay prefers given in technical Guides because it clearly distinguishes the starting digits from hints or instructional clues in Learn.
In product copy, “clue” can still be used when the meaning is obvious.
Coordinates
VeyraPlay uses row/column coordinates when a precise cell reference is useful.
For example:
r1c1= row 1, column 1r4c7= row 4, column 7r9c9= row 9, column 9
This notation is especially useful in technique Guides and example specifications.
A beginner should never need to memorize coordinates just to play. The UI can highlight the target cell visually while the coordinate provides a precise text reference.
How the grid creates Sudoku logic
Every cell participates in three units.
Imagine an empty cell at r4c7.
To decide whether 5 is a candidate, check:
- row 4
- column 7
- the 3×3 box containing
r4c7
If any of those units already contains a solved 5, then 5 cannot go in r4c7.
This simple overlap scales into the full solving system. Singles, Locked Candidates, subsets, Fish, Wings, and Chains all ultimately exploit constraints created by the grid.
How many cells can see a cell?
A cell has peers in its row, column, and box, with some overlap between those groups. The exact peer relationship matters more than memorizing a count when learning to solve.
For implementation and advanced explanations, the Sudoku engine should be able to query peers directly rather than relying on editorial assumptions.
FAQ
Is a box the same as a block?
In classic Sudoku, yes. Different resources use box, block, or region for the same 3×3 area. VeyraPlay prefers box.
What is a unit in Sudoku?
A unit is any complete row, column, or box.
What is a peer in Sudoku?
A peer is a cell that shares a row, column, or box with another cell.
Are the thick lines part of the rules?
They visually mark the boundaries of the nine 3×3 boxes. Those boxes are part of the classic Sudoku constraints.
What to learn next
Read Sudoku Rules if you have not already, then continue to Sudoku Candidates to see how the grid determines which digits remain possible in each cell.