One in Bonn

EIN

This German word means "a" or "one" and is often the first number learned in language classes.

"One in Bonn" is a clever play on German. "One" translates to "ein" in German, and Bonn is a city in Germany, so the clue hints at the German word for "one." The answer is "EIN," which fits both the literal meaning and the language reference. It’s a simple but effective example of how crosswords use foreign words for wordplay.