* Noun: When it refers to a plan or summary, like "I made an outline for my essay."
* Verb: When it means to sketch or make a plan, like "She outlined the key points of her presentation."
* Adjective: When it describes something that is like a summary or plan, like "We need an outline plan for the project."
So, to determine the part of speech, you need to look at the context of the sentence.