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.
Squares are quadrilaterals in which all four sides and all four angles have equal measurements. Rectangles have four angles with equal measurements, and the opposite sides also have equal measurements. All squares are rectangles, but not all rectangles are squares. Trapezoids have exactly one pair of parallel sides. Rhombuses have four sides with equal measurements, and opposite pairs of sides are parallel. All rhombuses are parallelograms, but not all parallelograms are rhombuses. All squares are rhombuses, but not all rhombuses are squares.