They are sometime congruent because a square is a parallelogram and its sides are congruent and a rectangle is one and its sides aren't congruent.
A parallelogram is a quadrelateral with opposite sides parallel and congruent.
A square. Parallelogram * * * * * No. It is a rhombus and a square is a special case of a rhombus. A parallelogram does not have four congruent sides, but two pairs of sides that are congruent to one another.
No. The congruent sides need not be parallel.
No, it is not.
No, you need both pairs of opposite sides to be congruent (i.e. the same size) to be a parallelogram.
A parallelogram (and all its special cases) has two pairs of opposite sides that are congruent. An isosceles trapezium has one pair of congruent opposite sides. Selected irregular quadrilaterals can have a pair.
Parallelogram, Rectangle, and Isosceles Trapezoid, opposite sides are congruent.
A parallelogram has two pairs of congruent sides (sides that have the same measure); for example, the top and bottom sides are congruent with one another, and the left and right sides are congruent with one another.
A parallelogram has two pairs of sides that are parallel when a trapezoid only has one. A parallelogram's opposite sides are congruent and opposite angles are congruent. A trapezoid has no opposite congruent sides or angles, unless it's an isosceles trapezoid, which base angles are congruent. They both have four sides and four interior angles that add up to 360 degrees.
Then, the opposite sides are congruent.