A
geometric shape consisting of
some number of
squares
attached at their edges. These are named for the number of squares in the shape,
e.g.,
monomino,
domino.
triomino, etc.
There is one monomino, a square.
There is one domino, a 1x2 rectangle.
There are two distinct triominoes, a straight chain of three squares, and a bent one. The bent triomino is the basis for Sid Sackson's game Tromino Go.
There are five distinct tetrominoes, or seven if you count reflections as distinct. These seven pieces were the basis for the game Tetris.
There are twelve distinct pentominoes. These pieces are the subject of many games and puzzles (especially tiling puzzles) in recreational mathematics.