a Quadrilateral
"...need to be the same SIZE?" Quadrilateral (including trapezium).
a polygon with 4 right angles and 4 sides of the same length
No.All 4 sides of a rhombus are the same length.
a polygon
square
A quadrilateral
a quadrilateral
A square.
There are infinitely many such shapes. A polygon with 4 or more sides can have two sides that are parallel and they need not be the same length.
rhombus
A trapezoid or a trapezium