Reversi Glossary

Reversi and Othello lean on a small, precise vocabulary: flank, flip, corner, mobility. Once you know these words, the rules and every strategy guide read like plain English. This glossary defines the terms you will meet across the whole Reversi family, from the basics of the board to the subtle endgame ideas that decide close games.

If you are brand new, skim this page before the rules. You do not need to memorise anything - just get a feel for the vocabulary, then read the full Reversi rules or the FAQ and the words will already make sense. Each term below has its own link, so other pages can point straight to a definition.

💡 Tip: Learn the four core ideas first - flank, flip, corner and mobility. Almost every rule and strategy you read is built from those four.

The basics

Reversi

The classic two-player strategy game of flanking and flipping discs on an 8x8 board. In its traditional form, players place the first four discs on the centre squares freely before normal play begins.

Othello

The standardised, trademarked version of Reversi, created in 1973. It uses the same rules but fixes the four opening discs in a diagonal cross, and it is the version played at the World Othello Championship.

Disc

A round playing piece, dark on one side and light on the other. Each player owns one colour, and a disc flips between colours as it is captured. The standard 8x8 game uses 64 discs, one per square.

Board

The grid of squares the game is played on - eight by eight (64 squares) in the standard game, but also 4x4, 6x6 or 10x10 in the variants.

Dark and light

The two colours (also called black and white). Dark always moves first. On this site you play the dark discs against the computer.

Flank

To trap a straight line of your opponent's discs between the disc you just played and another disc of your colour, in any of the eight directions. Flanking is what makes a move legal and triggers a capture.

Flip (capture)

To turn captured discs over to your colour. When you flank a line of enemy discs, every disc in that line flips. A single move can flip discs in several directions at once.

A move that flanks and flips at least one enemy disc. You may only play on a square that captures something - and if any legal move exists, you must make one; you cannot decline.

Pass (skip)

Forfeiting your turn because you have no legal move. Passing is forced, never a choice. If both players pass in a row, the game ends. See the passing FAQ.

Majority

Having more discs of your colour than your opponent. The player with the majority when the game ends wins; an equal split (32-32 on an 8x8 board) is a draw.

Opening

The first several moves of a game. In Othello the four centre discs are fixed in a diagonal cross; in classic Reversi the players place them freely, so games start from different shapes.

The board & its squares

Corner

One of the four corner squares. A disc in a corner can never be flanked or flipped, which makes corners the most valuable squares on the board and the anchors around which good play is built.

Edge

The outer ring of squares along the four sides of the board. Edge discs are harder to flip than central ones and, when anchored to a corner, become stable. Unanchored edges, though, can be split and flipped.

X-square

A square diagonally next to a corner. Playing an X-square before the neighbouring corner is settled usually lets your opponent take that corner for free, so it is one of the most dangerous moves in the game.

C-square

A square directly beside a corner along an edge. Like the X-square, a premature C-square move often hands the corner to your opponent. Both are covered in the danger-squares FAQ.

Centre

The four middle squares of the board, where every game begins. Strong players stay small and central early to keep their options open and give the opponent fewer discs to flank.

Strategy terms

Mobility

How many good legal moves you have. Keeping your mobility high while starving your opponent of moves is one of the strongest ideas in Reversi - it forces them into bad squares. See the mobility FAQ.

Frontier disc

A disc that sits next to an empty square, and so can be flanked. A position with many frontier discs is fragile; keeping your discs interior (surrounded by other discs) protects them.

Interior disc

A disc with no empty square beside it. Interior discs cannot be captured on the opponent's next move, so a compact interior position is safer than a sprawling one.

Stable disc

A disc that can never be flipped again for the rest of the game. Stability grows from the corners outward along anchored edges. The player with more stable discs, not more discs overall, usually wins the endgame.

Parity

Who is forced to move first, and who gets to move last, in each empty region of the board. Because the final disc into a pocket often flips the most, controlling parity frequently decides tight games. See the parity FAQ.

Tempo

The initiative - being the player who makes the other react. A quiet move that gains tempo, by giving you a move while removing one of your opponent's, is often worth more than any flip.

Quiet move

A low-key move that flips very few discs but improves your position - typically by preserving your mobility or forcing your opponent toward a bad square. In Reversi, quiet moves usually beat flashy, big-flip moves.

Wipeout (shutout)

A game that ends early because one player loses all their discs on the board, so the other colour occupies every remaining disc. Also called a shutout - rare, but a spectacular finish.

Variants & extras

Anti-Reversi (Misère)

A variant with the goal reversed: the player with the fewest discs at the end wins. Every normal instinct is inverted - corners can be traps, and you want your opponent to do the flipping. Play Anti-Reversi or read the Anti-Reversi FAQ.

Rolit

A four-colour party version of Reversi for up to four players, using the same flank-and-flip capture. A single move can flip several colours at once, and the player with the most balls of their own colour wins. Play Rolit.

Solved

A game whose perfect result from the start is proven. The 4x4 and 6x6 boards are solved second-player wins, and the standard 8x8 game was weakly solved in 2023 and shown to be a draw with perfect play. See the solved-boards FAQ.

Perfect play

Playing the theoretically best move in every position. No human plays Reversi perfectly, but the strongest computer programs come extremely close - far beyond the level of any human player.

Ready to use the vocabulary? Read the full Reversi rules, browse the FAQ, or just start a game.