What property of a parallelogram is included in the definition of a parallelogram?
A parallelogram is a quadrilateral with opposite sides that are parallel and congruent. Its opposite angles are congruent and its consecutive angles are supplementary.
The property in the def. is "a parallelogram is a quad with opposite sides parallel."
parallelogram has two LL 's in the word which show you two parallel lines l l which are two sides that are side by side and no matter how long you make the sides they will never touch and they are equal in length