Interjection

1. Yo Paulie! How's it going?

2. Yo, check this out!

3. Present! Here!

   Sergeant: Smith? Private Smith: Yo!

Contraction

1. contraction of you're

   Yo a fool.

Pronoun

1. shortened form of your.

   Yo sandwich only has bacon in it. Want some ketchup on that?

2. (Baltimore) third-person singular, familiar

   Yo was tuckin' in his shirt! (Stotko and Troyer 2007)