* Preposition: This is the most common usage. It shows a relationship between two things, similar to "about," "concerning," or "in relation to."
* Example: "I have some questions regarding the new policy."
* Gerund: This is a verb form ending in "-ing" that functions as a noun.
* Example: "Regarding the matter is important." (Here, "regarding" is the subject of the sentence.)
* Participle: This is a verb form ending in "-ing" or "-ed" that functions as an adjective.
* Example: "Regarding the matter, he decided to remain silent." (Here, "regarding" describes the matter.)
It's helpful to look at the context of the sentence to determine the specific part of speech.