* Verb (present participle): This is the most common use, describing an ongoing action: "The child is sliding down the slide."
* Adjective: Describing something that slides or is designed for sliding: "The car had sliding doors."
* Noun: Describing the action of sliding: "The sliding of the glacier caused a landslide."
Let me know if you have a specific sentence in mind and I can tell you the part of speech of "sliding" in that context!