A Sudoku Glossary: Every Common Term Explained

The board

• Cell: one of the 81 squares that holds a single value.
• Row: a horizontal line of nine cells.
• Column: a vertical line of nine cells.
• Box or region: one of the nine 3 by 3 squares.
• Group or unit: any row, column or box, since the rule applies to all three.

Starting position

• Clue or given: a value that is filled in at the start and cannot change. In Shapedoku these are the locked shapes.
• Solution: the one correct, completed board. A good puzzle has exactly one.

Notes and candidates

• Candidate: a value that could still legally go in a cell.
• Note or pencil mark: a small candidate you record inside an empty cell.
• Smart cleanup: automatically removing candidates that a new placement makes impossible.

Core techniques

• Scanning: sweeping rows, columns and boxes to find forced placements.
• Crosshatching: scanning one value across a single box to pin down its cell.
• Naked single: a cell with only one candidate left.
• Hidden single: a value that can go in only one cell of a group, even if that cell has other candidates.

Elimination techniques

• Naked pair: two cells in a group sharing the same two candidates, which lets you remove those candidates elsewhere in the group.
• Hidden pair: two values that can only go in the same two cells of a group.
• Pointing pair: a value limited to one line within a box, which lets you remove it from the rest of that line.
• X-Wing: a rectangle pattern across two rows and two columns that removes a candidate from those columns or rows.

Play and progress

• Mistake: a placement that breaks the rules or contradicts the solution.
• Hint: a reveal of one correct cell.
• Daily Challenge: a single fresh puzzle shared by everyone each day.
• Streak: the number of days in a row you have played.

Keep this page handy while you learn. Every term here shows up in real solving, and once the words are clear, the techniques become much easier to pick up. Try them out in Shapedoku whenever you are ready.