Concept in Definition ABC

At the behest of the Geometry we find two uses of the term apothem, on the one hand, when it comes to a polygon regular, for example of a hexagon, the apothem will be the lessdistance that exists between the center and any of the sides that compose it.
In this case it is a segment whose sides will be the center of the polygon and the midpoint of any of its sides. It should be noted that the apothem will always be perpendicular to the side in question from which it is drawn.

And on the other hand, in a pyramid regular, the apothem will be that segment that is drawn from the vertex towards the center of either side of the polygon that will form the base. It always matches the height of each of the triangular faces, in regular pyramids.

While, the radio, that in any circumference will be any segment that extends from its center to any point on the same circumference (half of the diameter), is divided into two segments, the sagite (It extends between the midpoint of a circumference arc and that of the chord) and the apothem, then, the sagite complements the apothem and the union turns out to be the radius.