The letter "ü" in German is always preceded by a vowel. This is because it represents a umlaut, a modification of the preceding vowel sound.
Therefore, words in German that contain "ü" will always start with a combination of a vowel and "ü", like:
* über (over)
* üben (to practice)
* Übung (exercise)
* übel (evil)
Let me know if you have any other questions about German grammar!