When you make posts, it would be good if we could all use the same terms. Please use these bolded words, if possible:

The puzzle grid consists of 9 rows (horizontally), 9 columns (vertically) and 9 3x3 boxes. Rows, columns and boxes are all kinds of unit. There are 27 units in a grid. Each unit must contain the digits 1 through 9.

Every unit contains 9 cells. Please don’t call the cells “squares”, because a box is square and the grid is square. The word “square” only causes confusion.

Three adjoining boxes in a line are a chute. If the chute is horizontal, it is a band. There are 3 bands: top, middle and bottom. If the chute is vertical, it is a stack. There are 3 stacks: left, middle and right. There are 6 chutes in a grid.

The numbers already in the grid are the puzzle’s clues. The numbers you add, as a player, are big numbers (as opposed to the small numbers you use temporarily, which are pencilmarks).

When you have an empty cell, the remaining numbers which could go into it according to the rules of the game are the empty cell’s candidates.

Boxes are numbered 1 to 9, in this layout:

1 2 3

4 5 6

7 8 9

Rows are numbered 1 to 9, top to bottom.

Columns are numbered 1 to 9, left to right.

A cell is referenced by its row and column number, e.g., r1c1 for the top-left cell, r5c5 for the center cell.

A row of 3 cells in a box is a mini-row or boxrow. A column of 3 cells in a box is a mini-col or boxcol.

The 9 occurrences of a given number in a solution are called a rookery. It follows that the 9 members of a rookery must each be on a different row and must each be in a different column.

If you do not stipulate otherwise, Classic Sudoku on a 9x9 grid is assumed.

- Wayne Gould (Pappocom)