What part of speech is alone?

"Alone" can be several parts of speech, depending on its function in a sentence:

* Adjective: Describing a state of being by oneself. Example: "She felt alone in the crowd."

* Adverb: Modifying a verb, adjective, or another adverb, indicating a state of isolation. Example: "He walked alone through the forest."

* Noun: Referring to the state of being alone. Example: "He preferred the alone to the company of others."

The most common usage is as an adjective, but the other possibilities exist depending on the context.