* Verb: This is the most common usage, meaning to combine or join something to something else.
* Example: "Please add the milk to the batter."
* Noun: This is less common, but it can refer to the act of adding.
* Example: "The add of sugar made the cake too sweet."
* Preposition: In rare cases, "add" can function as a preposition, meaning "in addition to."
* Example: "Add to the confusion, the phone started ringing." (This usage is uncommon and can be considered informal.)
It's important to look at the context to determine the part of speech of "add" in a specific sentence.