A piece in Tetris and similar games is a geometric shape consisting of a set of blocks that is moved as a unit. A block (or mino) is the part of a piece that fills one unit of the playfield. In some games, all blocks that make up a piece are colored the same; in others, especially falling piece games other than Tetris and its clones, they are colored differently.
A polyomino is a piece made of two or more square blocks, where all blocks are connected through full coincident edges (as if squares on graph paper).
- A free polyomino is one that may be translated (moved about), rotated, or reflected.
- A one-sided polyomino is one that may be translated or rotated.
- A fixed polyomino can only be translated.
Polyominoes come in several sizes:
- 2 blocks make a domino: (or dimino) featured in Dr. Mario and Puyo Pop; seen in Tetris Blast and Tetris Party.
- 3 blocks make a tromino (or trimino or triomino): featured in Columns (fixed I only) and Pac-Attack (L only); seen in Tetris Blast and Tetris Party (I, L) and Puyo Pop Fever (L only).
- 4 blocks make a tetromino (or tetramino or tetrimino), featured in all versions of Tetris and most clones. Lumines uses only O tetrominoes.
- 5 blocks make a pentomino (or pentimino), featured in Daedalian Opus; seen in Tetris 2 + Bombliss and Puyo Puyo Tetris (only I).
Polyominoes are often named by a Latin letter that resembles the shape of the polyomino. For instance, an "I" has all its blocks in a straight line, and a "T" consists of an "I" tromino with one or more blocks in a straight line connected to one side of the center of the "I". However, they have many other names as well.
Tetris Heaven occasionally drops a single large polyomino that is the exact size and shape for the playfield. However, be careful not to accidentally move or rotate it, or else.
| Hinged tetrominoes|
in Tetris 2
A hinged polyomino or polyplet is similar to a polyomino but also allows connections at a point. In games that use hinged polyominoes, a piece may break apart at the diagonal connections when it lands, and the fragments may or may not be controllable afterward.
- 4 blocks: Hinged tetromino (featured in Tetris 2).
Hextris and Bikaka are variants of Tetris that use 4-cell polyhexes, or pieces created from regular hexagons. Bubble Bath Babes uses polyhexes that may be reflected around the X or Y axis but not rotated.
In Puyo Puyo Tetris, it is possible to get a Piece consisting only of a single gold block. This monomino (also known as a mino) appears in Party and Fusion Modes. In Party, obtaining a certain item while playing Tetris will cause the next piece to turn into a monomino. In Fusion, a monomino can appear as part of certain dropsets. In Tetris Party, In beginner's tetris modes, Monominos are dropped, they are magenta colored.
L & I variants
In Tetris Party's beginner's tetris modes, there are multiple "small pieces"
- L3 pieces are L pieces, but without the extra piece on the end, they are colored cobalt blue.
- I3 pieces are Trominos that are 3 blocks long, they are colored grayish-green