Word Origin & History. epicene mid-15c., originally a grammatical term for nouns that may denote either gender, from L. epicoenus common, from Gk. Extended sense of characteristic of both sexes first recorded in English c.1600; that of effeminate 1630s.
A parallelogram is a quadrilateral with two pairs of parallel sides. Equivalent conditions are that opposite sides are of equal length; that opposite angles are equal; or that the diagonals bisect each other. Parallelograms also include the square, rectangle, rhombus and rhomboid. Rectangle: all four angles are right angles. 2  An equivalent condition is that the diagonals bisect each other and are equal in length. 3  Informally: a box or oblong (including a square). 4  Square (regular quadrilateral): all four sides are of equal length (equilateral), and all four angles are right angles.
Since the sum of the interior angles of any triangle is 180Â° and there are two triangles in a quadrilateral, the sum of the angles for each quadrilateral is 360Â°. Specific Types of Quadrilaterals. Letâs start by examining the group of quadrilaterals that have two pairs of parallel sides. These quadrilaterals are called parallelograms They take a variety of shapes, but one classic example is shown below. Imagine extending the pairs of opposite sides.