General:
* Quadrilateral: This is the most general term, simply meaning a four-sided figure. It doesn't specify any specific properties.
* Trapezium: This is a more common term in British English, but it can also mean a quadrilateral with no parallel sides in some contexts.
Focusing on parallel sides:
* Trapezium (British English): This term often implies the existence of one pair of parallel sides.
Focusing on specific types:
* Isosceles Trapezoid: This term is used when the two non-parallel sides are equal in length.
* Right Trapezoid: This term is used when at least one of the non-parallel sides is perpendicular to the parallel sides.
The best choice will depend on the context and the specific properties you want to emphasize.