* Noun: When referring to the smell itself.
* Example: "The scent of roses filled the air."
* Verb: When referring to the act of smelling something.
* Example: "The dog scented the trail."
* Adjective: When describing something that is related to smell.
* Example: "They used scent markers to follow the trail."
So, to determine the part of speech, look at the context of the sentence!