Set Equivalence Theory

Set Equivalence Theory (SET) is an application of Sudoku that establishes an equivalence relationship between cells in different regions of a Sudoku grid. Some of the most common examples of Set Equivalence Theory include the Phistomefel Ring and Aad van de Wetering's Tetro Trick.

Set Equivalence Theory is a very useful technique in sudoku variant puzzles. It is often used for balancing sums with arrows and killer cages. Other ways SET can be useful is to make finding x-wings, swordfishes, and jellyfishes easier, as well as finding franken-fishes and mutant-fishes.

Trivia

 * Set Equivalence Theory is a recursive acronym
 * Philip Newman came up with the term Set Equivalence Theory