square
Lots of objects do not have supplementary angles. It does them, or their environment, no harm.
half of a clock
A ramp, hill
Prefices are used to indicate the number of sides, angles, faces or solid angles (in 3d objects).
Square, rectangle and a right angle triangle are examples.
Vertical angles are used in construction, computer design, and just about any other field where objects are built. Angles add design and strength.
cubism
There are infinitely many such shapes.
They are both 2 dimensional objects with five straight sides and five angles. The sum of the internal angles is 540 degrees, the sum of the exterior angles is 360 degrees.
One example is hinges on a door that is wide open.
Regular geometric objects such as polygons have all sides and angles of identical size.
A reflex angle is greater than 180 but less than 360 degrees