An apothem is a line segment that extends from the center of a regular polygon to the midpoint of one of its sides. It is perpendicular to that side, effectively acting as the height of the triangle formed by the apothem and two radii of the polygon. The apothem is crucial in calculating the area of regular polygons. In geometry, the area of a regular polygon can be found using the formula: Area = (Perimeter × Apothem) / 2. The apothem is particularly important for shapes like pentagons, hexagons, and octagons, where all sides and angles are equal, making it easier to determine their area.