* Preposition: This is the most common usage. It shows the relationship between a noun or pronoun and another element in the sentence.
* "The book was written by Jane Austen."
* "I walked by the park."
* Adverb: "By" can indicate means or manner.
* "He won by a landslide."
* "Please speak by the phone."
* Conjunction: In some cases, "by" can function as a conjunction, connecting two parts of a sentence. This is less common but can be found in phrases like:
* "By and by, the sun rose."
* "We'll know by then."
Therefore, to determine the part of speech for "by", you need to look at its context within the sentence.