* Noun: This is the most common usage. It refers to a sudden strong urge or desire to act.
* Example: "He acted on a sudden impulse and bought the expensive watch."
* Verb: It can be used as a verb meaning "to stimulate" or "to urge."
* Example: "The electrical current impulses the muscle to contract."
* Adjective: While less common, it can act as an adjective meaning "sudden" or "unplanned."
* Example: "She made an impulse purchase at the grocery store."
To determine the part of speech, you need to consider the context of the sentence.