Pembenne ni umbo bapa lenye pande nne. Kwa lugha nyingine ni pembenyingi yenye pembe nne. Pembenne hutokea kama nukta nne kwenye tambarare zaunganishwa kwa mistari inayofunga eneo ndani yao. Maumbo ya pekee ya pembenne ni mstatili, mraba, trapeza na msambamba. Kila pembenne huwa na ulalo mbili. Jumla ya pembe zote ndani ya pembenne ni nyuzi 360°. Wikimedia Commons ina media kuhusu: Pembenne Compendium Geometry Analytic Geometry of Quadrilaterals Quadrilaterals Formed by Perpendicular Bisectors, Projective Collinearity and Interactive Classification of Quadrilaterals from cut-the-knot Definitions and examples of quadrilaterals and Definition and properties of tetragons from Mathopenref Venn Diagram of Quadrilaterals An extended classification of quadrilaterals Archived 30 Desemba 2019 at the Wayback Machine. at Dynamic Math Learning Homepage Archived 25 Agosti 2018 at the Wayback Machine. The role and function of a hierarchical classification of quadrilaterals Archived 19 Julai 2011 at the Wayback Machine. by Michael de Villiers