* Noun: This is the most common usage, referring to a film or video that presents factual information.
* Example: "I watched a fascinating documentary about the Amazon rainforest."
* Adjective: Describing something as relating to or resembling a documentary.
* Example: "The documentary evidence was compelling."
* Verb: Less common, but it can be used to mean "to create a documentary about something".
* Example: "They're documenting the lives of people living in remote villages."
Let me know if you have a specific sentence in mind and I can tell you which part of speech it is in that case!