What is a Naked Single in Pencil Notes?
All the strategies, starting with this one, use pencil notes to find the correct answer.
A Naked Single occurs when you look at a specific cell and realize that, after eliminating all impossible numbers, only one candidate remains.
It is called “Naked” because it sits completely alone in the cell, exposed and obvious, without any other competing numbers around it.
A Step-by-Step Example
Take a look at the pencil notes on this example grid. Can you spot a Naked Single here?
- Examine the cell: Look closely at the highlighted cell in our example below.
- Spot the lone candidate: While other cells around it might contain three or four potential numbers, we can see that the highlighted cell has only one possible number, and it is 2.
- Fill the cell: Since no other options exist for this specific spot, you can confidently write down the number 2 as the permanent answer.
Scanning Rows, Columns, and Blocks
Don’t limit your search to just one area of the board. A Naked Single is property of a single cell, but it can be discovered anywhere on the grid:
- In a Block: A cell inside a 3×3 square has only one candidate left.
- In a Row or Column: Naked Single can also be applied in a column or row. When you look across a long line of cells, you might find that a particular cell has been stripped of all other options due to the numbers present in the intersecting units.
Why Pencil Notes Change the Game
Switching to pencil notes is the turning point for every serious Sudoku player. It transforms the game from a test of pure observation into a game of logical deduction.
Ready to practice with notes? Open up one of our Sudoku Puzzles, turn on the “Notes” feature in the game tools, and start hunting for those lone candidates!