A parallelogram, in plane geometry, is a plane figure of four sides whose opposite sides are parallel to each other and where each side is equal in length to its opposite side. This four-sided figure is called a polygon (a two-dimensional [2D] figure formed of three or more straight sides) or, more specifically, a quadrilateral (a 2D figure formed of four straight sides).
In all types of parallelograms, the diagonals cut each other in half (or, bisect each other) where they intersect. (A diagonal is a line that joins two opposite corners of a geometric figure, such as a parallelogram.)
Three special types of parallelograms are called the rhombus, the rectangle, and the square.
A rhombus is a parallelogram with all four sides of equal length but the sides to not necessarily meet at right angles to one another.
A rectangle is a parallelogram whose adjacent sides are perpendicular (meet at right angles) to one another and opposite sides are equal in length.
A square is a parallelogram whose adjacent sides are both perpendicular (angled at 90°) and equal in length. That is, all four sides are equal in length and the sides that contain a common point are at right angles to one another.
The area (A) of a parallelogram is equal to the distance (length) of one side, called its base b, times the shortest distance (length) to the opposite side, called its altitude or height h. It can be notated as A= bh. Since all four sides (s) of a square are equal, then b= h= s, and its equation can be written A= 2s. The circumference (C) of a parallelogram (or the distance around it) is denoted: C= 2b+ 2H. In the case of a square (where all four sides are equal in length), the equation becomes: C= 4s.
A parallelogram is a plane figure of four sides whose opposite sides are parallel . A rhombus is a parallelogram with all four sides of equal length; a rectangle is a parallelogram whose adjacent sides are perpendicular ; and a square is a parallelogram whose adjacent sides are both perpendicular and equal in length.
The area of a parallelogram is equal to the length of its base times the length of its altitude.
par·al·lel·o·gram / ˌparəˈleləˌgram/ • n. a four-sided plane rectilinear figure with opposite sides parallel.