thunderbolt

thumb|The high-voltage|high-voltage electricity warning symbol is a contemporary example of thunderbolt iconography

A thunderbolt, or lightning bolt, is a symbolic representation of lightning. It appears variously in history, literature, and in contemporary warnings of (typically high-voltage) electricity. Thunderbolts may appear naturally among the estimated 8.6 million lightning strikes per day or not: heat lightning is an electrical discharge in the atmosphere without an accompanying sound, and a Tesla coil produces an artificial "lightning"-like electrical discharge with an accompanying clap. The term "thunderbolt" adds the notion of a loud thunderclap accompanying a lightning flash, while the term "lightning bolt" — which refers directly to the electrical discharge — does not.