LEPTON is from the Greek word “leptos” ... it means “small” or “fine.” In English it signifies a small sub-atomic particle like a muon (not to be confused with the much, much larger mesons!). A muon has a mass 207 times less than an electron an exists for 2.2 times ten to the minus six second. In more modern times, a LEPTON was a small Greek coin worth one-hundredth of a drachma and, when you went shopping, would last about 2.2 seconds.