* Noun: This is the most common usage, referring to the power or right to give orders, make decisions, and enforce obedience.
* Example: "The doctor has the authority to prescribe medication."
* Adjective: Describing something as having power or influence.
* Example: "She is an authority on ancient history."
* Verb: Less common, but meaning to authorize or give power to.
* Example: "The company authorized the project."
It's important to look at the context of the sentence to determine the correct part of speech.