This handy part of speech includes words such as in, on, by, to, since, and from. Prepositions work as modifiers for nouns, verbs, and adjectives helping to clarify spatial and temporal relationships.
Can be confused
The often heard but misleading “rule” that a sentence should not end with a preposition is transferred from Latin, where it is an accurate description of practice. But English grammar is different from Latin grammar, and the rule does not fit English. In speech, the final preposition is normal and idiomatic, especially in questions: What are we waiting for? Where did he come from? You didn't tell me which floor you worked on. In writing, the problem of placing the preposition arises most when a sentence ends with a relative clause in which the relative pronoun (that; whom; which; whomever; whichever; whomsoever) is the object of a preposition. In edited writing, especially more formal writing, when a pronoun other than that introduces a final relative clause, the preposition usually precedes its object: He abandoned the project to which he had devoted his whole life. I finally telephoned the representative with whom I had been corresponding. If the pronoun is that, which cannot be preceded by a preposition, or if the pronoun is omitted, then the preposition must occur at the end: The librarian found the books that the child had scribbled in. There is the woman he spoke of.