What has no beginning, end, or middle?

Why this works

This riddle plays on the concept of shapes and their properties. A doughnut (or a circle) is a continuous form that loops back on itself, meaning it has no distinct starting point, no ending point, and no central point that divides it. The cleverness lies in how we perceive beginnings and ends in a linear context—here, the shape defies that by being a closed loop, emphasizing its unique structure.