Breakdown:
* Usted: Formal "you" (used when addressing someone with respect, like an elder or someone you don't know well).
* es: "is" (third person singular present tense of "ser")
* un: "a" (indefinite article)
* niño: "child"
Note: It's important to remember that using "usted" with someone younger than you can sometimes be considered condescending or patronizing. In most situations, using "tú" (informal "you") would be more appropriate.