- 四角形 sìjiǎoxíng quadrilateral; tetragon(geometry) quadrangle; a four-sided polygon, also known as a [[四边形|四邊形|si4 bian1 xing2]]
- 四角号码 sìjiǎohàomǎ Four-Corner SystemA method of indexing and inputting Chinese characters based on the shapes of their four corners
- 四角帽 sìjiǎomào four-cornered hatA four-cornered cap or hat, such as a biretta
- 四角柱体 sìjiǎozhùtǐ cuboida cuboid or rectangular prism in mathematics
- 四角裤 sìjiǎokù boxer shortsboxer shorts; trunks
