eureka

1. a cry of joy or satisfaction when one finds or discovers something.

   The answer hit me. ‘Eureka!’ I cried

   there weren't many eurekas but science is moving steadily

   the eureka moment for him came when he was hill-walking

noun

an alloy of copper and nickel used for electrical filaments and resistance wire.

early 17th century: from Greek heurēka ‘I have found it’ (from heuriskein ‘find’), said to have been uttered by Archimedes when he hit upon a method of determining the purity of gold. The noun dates from the early 20th century.