Why is the st. louis arch considered a real life parabola?

please give reasons why it is considered a real life parabola!Why is the st. louis arch considered a real life parabola?
It looks like a parabola, but it's not. The Gateway Arch in St. Louis is an inverted catenary. A catenary is the curve of a hanging chain. (See the hanging chain images below.) Galileo thought this curve was a parabola, so don't feel bad if you were also fooled. The catenary shape minimizes the potential energy throughout the chain. When shifted, a hanging chain will naturally return to this position. At each point in a hanging chain or arch, the opposing forces (chain: tension forces, arch: compression forces) are balanced. This creates stability.



The catenary equation is where a is determined by the linear density and tension of the chain. This is a transcendental curve rather than an algebraic curve like the parabola. The catenary is a hyperbolic function: .







BUT!!!!!!!!!!!!!!!

it looks like one indeedWhy is the st. louis arch considered a real life parabola?
There isn't much to this. A parabola has a definition. The St. Louis arch fits this definition. Why not call it a real life parabola?