Question

Is a rectangle a parallelogram always, sometimes or never?

Answer 1

Compare a rectangle and a parallelogram:

A parallelogram is a rectangle. It is true when the parallelogram has these properties listed below. It is not true when a parallelogram has no right angle. A quadrilateral (a polygon with $4$ vertices) $ABCD$ with pair of opposite sides parallel to each other that is $AB$ is parallel to $CD$ and $BC$ is parallel to $AB$ is called parallelogram

The properties of rectangle are

1. $4$ right angles
2. $2$ pair of opposite congruent sides
3. Congruent diagonals
4. $2$ sets of parallel sides
5. Mutually bisecting diagonal

Hence, a rectangle is always a parallelogram.