An arrangement of overlapping circles which cover the entire plane. A lower bound for a covering using equivalent circles is 
(Williams 1979, p. 51).
Circle Covering
See also
Circle Covering by Arcs, Circle Packing, Disk Covering Problem, Five Disks Problem, Flower of Life, Seed of LifeExplore with Wolfram|Alpha
References
Williams, R. "Circle Coverings." §2-6 in The Geometrical Foundation of Natural Structure: A Source Book of Design. New York: Dover, pp. 51-52, 1979.Referenced on Wolfram|Alpha
Circle CoveringCite this as:
Weisstein, Eric W. "Circle Covering." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/CircleCovering.html