Levity Was Once a Scientific Term

Levity originally was thought to be a physical force exactly like gravity but pulling in the opposite direction, like the helium in a balloon. As recently as the 19th century, scientists were still arguing about its existence. Today levity refers only to lightness in manner. To stern believers of some religious faiths, levity is often regarded as almost sinful. But the word, like its synonym frivolity, now has an old-fashioned ring to it and is usually used only half-seriously.