Some words have fallen out of popular usage. Who says "that's groovey," or "thanks, daddio?" Even to approve of something by saying "that's swell" is confined to old movies and TV shows. But there is a serioius problem when one of the most important words in the world falls into disuse. This is especially troublesome when the concept expressed by that word is vital to grasp in order for us to prepare for time and eternnity. "Sin" is such a word. It is rarely uttered. But we must understand it.