Tic tac toe, whose name has several variations according to its players' geographical location, is a simple game that all children have once given a try. Its name has a fairly straightforward etymology, yet a long history possibly dating back to the Roman Empire.

Features
Tic tac toe is a game played by two players, identified respectively as "X" and "O." The playing board is a three row by three column grid drawn with pencil on paper. The players alternate marking X and O within the nine squares of the grid, each intending to create a row of three marks either horizontally, vertically or diagonally. X usually goes first. Because the grid is so small and strategizing relatively easy, the game is mostly played by children.

Identification
"Tic tac toe" has a few other accepted spellings: tick tack toe, tick tat toe and tit tat toe, among others. Hyphenation of the word is also acceptable (tic-tac-toe). In England the game is commonly called "noughts and crosses." Depending on the region in Ireland, "X's and O's," "X-e O-zees" and "Boxin' Oxen" are also used. Norway calls it "Twiddles and Bears."

History
The game itself is thought to date to the Roman Empire. The 3 by 3 grid of a game called Terni Lapilli has been found scratched into surfaces. But because no markings have ever been discovered within the grid, evidence suggests the game might have been played with pieces placed on top.

The name tic tac toe comes from a game by the same name, no longer played, in which players with their eyes closed tossed a pencil down onto a slate marked with numbers, and earned the score the number indicated--something like blind darts. The game dates to the mid- to late 1800s. "Ticktack," according to the Random House Dictionary of English language, is a repetitive sound made by repetitive tapping, knocking or clicking. Thus, "tic tac toe" is an imitation of the sound the pencil makes when hitting the slate.

Size
Because of its mathematical simplicity, it is simple to create a computer game that simulates tic tac toe perfectly. Examining the probability of possible games, it is possible to place X's and O's on the grid (in winning and nonwinning combinations) in 362,800 unique configurations. There are 255,168 possible winning configurations. There are, however, only 138 unique winning outcomes if symmetrical plays are eliminated from the equation.

Potential
Other slightly more complex variations exist that involve tic tac toe's main objective: being the first player to form a row of so many marks. Connect Four is a popular one, as well as Three Men's Morris, Nine Men's Morris, Pente, Qubic and Quarto.