A right angle triangle
Any polygon, if it is not regular, can have 1 right angle.
right angle triangle
Any polygon can have just one right angle, from a right angled triangle upwards.
Any polygon can have one right angle, for example, a right angled triangle.
Any polygon can have a right angle. A right angled triangle is an example.
A right triangle.
An irregular septagon: the right-angle will prevent it being regular.
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A polygon is pretty much any enclosed shape constructed of straight line segments connected end to end. The angles do not have to be right. In fact, they usually aren't. A right angle would NEVER be a polygon, as it is just one right angle. In Euclidean geometry a right angle must be accompanied by two acute angles to form a triangle--the polygon with the smallest number of sides.
Any polygon with 4 or more sides can always have a right angle.
There is no specific name, but "right-angled polygon" will suffice.
A right scalene triangle.