If both pairs of opposite sides are the same length, and both pairs of opposite angles are the same, the quadrilateral is a parallelogram (rhombus, rectangle, or square).
square
Parallelogram. You could also call it a rhombus if all sides are the same length, but a rhombus is technically a parallelogram.
A parallelogram.
rhombus. The rhombus is a quadrilateral with all sides equal in length. It is also a parallelogram, so opposite sides are parallel and equal in length, and opposite angles are equal.
Square
QUADRILATERAL
If both pairs of opposite sides are the same length, and both pairs of opposite angles are the same, the quadrilateral is a parallelogram (rhombus, rectangle, or square).
A Rhombus
square
Parallelogram. You could also call it a rhombus if all sides are the same length, but a rhombus is technically a parallelogram.
A rectangle is a quadrilateral with four right angles and opposite sides that are equal in length. The diagonals of a rectangle are also equal in length and bisect each other at 90 degrees.
Most quadrilaterals do not have opposite sides which are equal in length. Sadly, there is no special name for them.
A Rectangle
A parallelogram.
A parallelogram.
a pentagon