Does the Prefix “-un” Usually Mean a Reversal?

Sarah in San Antonio, Texas, says that when she goes to a restaurant and orders iced tea, the server usually asks, “Sweet or unsweet?” That doesn’t sound right to her. How do you unsweeten tea? Doesn’t the un- imply a “reversal of a state”? Not necessarily. You can have something unfolded that was not previously folded, something unbuilt that was never built, and something unbelievable that never was believable. Particularly with adjectives, the prefix un- doesn’t always imply a reversal. Sometimes it simply connotes the idea of “not” or suggests “the absence of a condition.” This is part of a complete episode.