What is a tetromino?

Tetromino is the proper name for a Tetris piece. It is a small idea from recreational math that happens to be the atom of the whole game.

Below you will find the short version first, then a fuller walkthrough with clear Tetris examples, a few closely related questions, and a link to try it yourself. Everything here is free to play right in your browser.

The short answer: A tetromino is a geometric shape made of four squares joined edge to edge. Counting rotations as the same shape, there are five free tetrominoes, but Tetris treats mirror images as different, giving the seven pieces you play with. The word comes from tetra, the Greek for four.

Four squares, seven pieces

A tetromino is any figure you can build from four unit squares connected along their edges. If you allow flips, only five distinct shapes exist, but Tetris counts the mirror pairs S and Z, and J and L, separately. That gives the seven playable pieces, each explained in the piece names guide.

Tetromino vs tetrimino

You will see two spellings. Mathematicians write tetromino, following domino and pentomino, while The Tetris Company trademarked the spelling Tetrimino for its official pieces. Both refer to the same four-cell shape, so the difference is branding rather than geometry.

Where the math comes from

Tetrominoes belong to the family of polyominoes, shapes made of any number of joined squares, popularized by mathematician Solomon Golomb. The four-cell case is small enough to fit a play well yet varied enough to create endless stacking puzzles, which is exactly why it powers the game. You can browse the terms in the glossary.

Drop some tetrominoes

People also ask

What are the Tetris pieces called?

The seven Tetris pieces are named after the letters of the alphabet they look like: I, O, T, S, Z, J and L. The I is the long bar, the O is the square, and the rest are bends and elbows. Modern guideline Tetris gives each piece a fixed color so you can recognize it instantly.

Why is it called Tetris?

The name Tetris blends two words. The first is tetra, the Greek prefix for four, because every piece is made of exactly four cells. The second is tennis, the favorite sport of inventor Alexey Pajitnov. He combined the two into Tetris, and the four-based name has fit the game perfectly ever since.

What is SRS rotation in Tetris?

SRS stands for the Super Rotation System, the official guideline standard for how pieces rotate. It fixes each piece's rotation states and, crucially, adds wall kicks, which nudge a piece sideways or up when a plain rotation would be blocked. SRS is what makes moves like the T-spin possible and consistent across modern Tetris games.