* Adverb: When it indicates location or direction, like "The cat is there."
* Expletive: When it's a filler word that doesn't have a grammatical function, but helps with sentence structure, like "There are many stars in the sky."
* Pronoun: In certain contexts, it can function as a pronoun, like "The book is there on the shelf."
To determine the correct part of speech, you need to consider the context of the sentence.