In physics, and electronics, the henry (symbol H) is the SI unit of inductance.[1] It is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction. (In England, Michael Faraday (1791–1867) discovered the same thing independently. They discovered it at about the same time.)[2] The magnetic permeability of a complete vacuum is 4π×10−7 H/m (henry per meter).
The National Institute of Standards and Technology provides guidance for American users of SI to write the plural as henries. People do not capitalize unit names.