Sudoku (noun)

A type of logic puzzle that involves filling in a grid of digits so that each column, each row, and each of the subgrids that compose the grid contains all of the digits from 1 to 9.

Origin:

A puzzle invented by howard garns, later became popular in japan in the late 1980s and called sudoku, which is short for 数独 (sūdoku) meaning "single number".

Examples:

1. I spend my morning solving sudoku puzzles.
2. The sudoku competition was held in a local park.
3. I always have a sudoku book in my bag for when I'm waiting in line.
4. The difficulty of the sudoku puzzles increases as you progress through the book.
5. Many people find sudoku to be an enjoyable and challenging way to exercise their brain.