Here's why:
* Suburb is a word that describes a residential area on the outskirts of a city.
* The root word urb comes from the Latin word "urbs," meaning "city."
* The prefix sub means "below" or "under," indicating that a suburb is located below or under the main city area.
Therefore, "-urb" is the suffix that completes the word "suburb" and refers to the city or urban area.