A right triangle.
If it has no right angle then a scalene triangle would fit the given description
a rhombus, a quadrilateral without right angle, a quadrilateral with equal opposite parallel sides but no right angles
It is the right angle triangle which has 3 sides whereas all quadrilaterals have 4 sides.
A rectangle has four sides whereas a right angle triangle has only three sides.
A right triangle.
If it has no right angle then a scalene triangle would fit the given description
a rhombus, a quadrilateral without right angle, a quadrilateral with equal opposite parallel sides but no right angles
It is the right angle triangle which has 3 sides whereas all quadrilaterals have 4 sides.
It could be an isosceles right triangle, or it could be a non-regular specimen of any polygon with more than three sides.
If this makes sense.... something like this |\ | \ |___\ A three sided polygon that has one right (90 degree) angle and all three sides have different lengths
A rectangle has four sides whereas a right angle triangle has only three sides.
There are three sides.
A right triangle has three sides and one right angle.
A right angle triangle
Any polygon with more than three sides may have an angle greater than 180 degrees.
An equalateral triangle