Is a quadrilateral a trapezoid

Answer 1

No, a quadrilateral isn't always a trapezoid. One way to consider it is that all trapezoids are quadrilaterals (four-sided shapes), but not all quadrilaterals are trapezoids.

Some quadrilaterals are concave quadrilaterals, some are scalene convex quadrilaterals (called trapezoids in the UK), some would be trapezoids, and some would be parallelograms (rectangles, squares, rhomboids, rhombi).

If parallelograms are considered a special case of trapezoids, then trapezoids would include all non-scalene convex quadrilaterals, which is a highly inclusive definition.