na-adjective, noun which may take the genitive case particle 'no', noun
Refers to a four-sided shape, especially a square or rectangle. In geometry, it can mean any quadrilateral. Also used adjectivally to describe something as square-shaped.
この箱は四角い形をしている。
This box has a square shape.
紙を四角に切ってください。
Please cut the paper into a square.