What is a hexagon? Having a slight parenting anxiety attack and I hate teaching my son something incorrect.
Wiktionary tells me that a Hexagon is a polygon with $6$ sides and $6$ angles.
Why the $6$ angle requirement?  This has me confused.
Would the shape below be also considered a hexagon?


A  hexagon is a simple closed polygon $P$ (presumably in the plane) with $6$ sides. Simple means that the sides are arranged in cyclic order, that two subsequent sides have exactly one point, called a vertex, in common, and that otherwise the sides don't intersect. Maybe you want to include the condition that subsequent sides should not be parallel.  Jordan's curve theorem then guarantees that $P$ has a well defined interior (an "open hexagon") and an exterior which extends to infinity.
The polygon in your figure is a hexagon according to this definition. If you want to exclude it you would have to  explicitly require that the considered hexagon be convex. (Maybe you can use this opportunity to make your son familiar with the notion of convexity $\ldots$)
