Radial symmetry is the property of being symmetrical in all directions. Round is the most perfect radial symmetry. Hexagons are radially symmetric, and can fit together without spaces. Octagons are radially symmetrical, and can be combined to form a radially symmetric shape, but not without interstices, and they will have symmetrical sections made of multiple octagons, not individually symmetrical.
See also: FractalTiling