Naked single
A cell has only one possible digit.
A technique for Easy puzzles. Play a Easy puzzle
What it does
Look at one empty cell and cross off every digit already in its row, column and box. If only one digit is left, that is the answer.
How to spot it
Cells in crowded rows, columns and boxes are the best places to look. With your notes written in, it is any cell with a single candidate. Later in a puzzle, other techniques remove candidates until a naked single appears.
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What it lets you do
You place the only digit left in the cell.
Try it
Find the Naked single on this board. Pick its cell, then choose its digit.
Practise it
The best way to learn a technique is to meet it in a real game. Practice puzzles are sure to need it, at Easy level; any Easy puzzle may need it too.