* Preposition: When used to indicate location or position, like "The cat is outside."
* Adverb: When modifying a verb, adjective, or another adverb, like "Let's eat outside."
* Noun: When referring to the exterior of something, like "The outside of the house is painted red."
* Adjective: In rare cases, it can be an adjective, like "The outside temperature is freezing."
The specific part of speech depends on its function within the sentence.