Noun
A right-lined quadrilateral figure, whose opposite sides are parallel, and consequently equal; -- sometimes restricted in popular usage to a rectangle, or quadrilateral figure which is longer than it is broad, and with right angles.
Source: Webster's dictionaryDrawing with three points of a parallelogram Rytz’s construction can be used to find the minor and major axes and their angle of an ellipse from conjugate diameters (which can be seen as three points of a parallelogram). Source: Internet
Any line through the midpoint of a parallelogram bisects the area. Source: Internet
For example, adjacent angles of a parallelogram are supplementary, and opposite angles of a cyclic quadrilateral (one whose vertices all fall on a single circle) are supplementary. Source: Internet
Conjugation distributes over the standard arithmetic operations: : : : : Addition and subtraction Addition of two complex numbers can be done geometrically by constructing a parallelogram. Source: Internet
An equivalent condition is that opposite sides are parallel (a square is a parallelogram), that the diagonals perpendicularly bisect each other, and are of equal length. Source: Internet
In three dimensions, it is further possible to define a cross product which supplies an algebraic characterization of the area and orientation in space of the parallelogram defined by two vectors (used as sides of the parallelogram). Source: Internet