"Up" can be a verb in certain cases:
* To increase: "Prices are up this year."
* To rise: "The sun is up."
* To improve: "My spirits are up."
* To be awake: "Are you up yet?"
However, "up" is more commonly used as:
* A preposition: "The ball went up in the air."
* An adverb: "He looked up at the sky."
* Part of a phrasal verb: "Wake up," "Give up," "Clean up."
So, "up" can be a verb, but not always. It's important to consider the context of the sentence to determine its function.