thumb|right|upright=1.7|The 12 pentominoes can form 18 different shapes, with 6 of them (the chiral pentominoes) being mirrored.
thumb|right|upright=1.7|The 12 pentominoes can form 18 different shapes, with 6 of them (the chiral pentominoes) being mirrored.
A pentomino (or 5-omino) is a polyomino of order 5; that is, a polygon in the plane made of 5 equal-sized squares connected edge to edge. The term is derived from the Greek word for '5' and "domino". When rotations and reflections are not considered to be distinct shapes, there are 12 different free pentominoes. When reflections are considered distinct, there are 18 one-sided pentominoes. When rotations are also considered distinct, there are 63 fixed pentominoes.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).