прва

In a sentence

• Прва кућа на улици је моја.

  The first house on the street is mine.

  Here, 'прва' is used as an ordinal number meaning 'first,' describing the position of the house on the street.

• Она је прва која је стигла.

  She is the first one who arrived.

  In this sentence, 'прва' is again ordinal but refers to a person being the first to perform an action (arriving).

• Ово је моја прва симфонија.

  This is my first symphony.

  Here, 'прва' denotes the sequential position of a creation among others, indicating that it's the first work the speaker composed.