Valid

A valid or proper Sudoku has a unique solution, otherwise it is an invalid Sudoku.

Opinions differ about the use of this qualifier. Some players state that the name Sudoku implies that there is a unique solution. A puzzle with multiple solutions only looks like a Sudoku.

The topic in this article is a still a subject of debate. Parts of the text may not express everybody's opinion. Use the associated Talk page if you do not agree with the opinion of the writer, rather than continuously editing the main article.