There has been some confusion about this, it's a
good question. The term "lepton"
comes from the Gospels, and contextually refers to a paltry
denomination equal to half a
quadrans. Indeed, the Greek word "lepton" refers to something small or thin.
The
prutah is a rabbinic term, which we also discern from context must have been a small
denomination. The relationship between the lepton and the
prutah has not been determined with certainty. Some authors describe the lepton as a half-prutah (if such a thing exists!), while others consider them to be the same
denomination.