Single

Elementary solving technique, using the fact that only a single candidate is left for a constraint.

Singles are often ignored when players communicate about the way they solve a Sudoku. Singles are the only solving techniques which deal with immediate placements. Other techniques can only accomplish eliminations, but may lead to an immediate single.

There are 2 types of singles:

Naked Single

Only a single candidate left in a cell.

Hidden Single

Only a single candidate left for a particular digit in a house.