parallelogram is a quadrilateral in which opposite sides are parallel
Parallelogram In Euclidean geometry, a parallelogram is a simple (non-self-intersecting) quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure. The congruence of opposite sides and opposite angles is a direct consequence of the Euclidean parallel postulate and neither condition can be proven without appealing to the Euclidean parallel postulate or one of its equivalent formulations.
Interventricular septum The ventricular septum is directed obliquely backward to the right, and curved with the convexity toward the right ventricle; its margins correspond with the anterior and posterior longitudinal sulci.