A preposition defines the relationship between two or more nouns, noun phrases, or verbs in a sentence. Many prepositions are monosyllabic words such as off, on, in, up, and down. Others are compounds originating from two separate words—for example outside, upon, throughout, and underneath. Others are multiple separate words (e.g., with regard to, in front of), and still others are participles (e.g. during, regarding, assuming).
A prepositional object is a noun, pronoun, or noun phrase that is linked by a preposition to other elements of a sentence. For example, in the sentence, I don’t want to go on the plane, the noun phrase the plane is the object of the preposition on. In the sentence, I’m going on a date with him, the noun phrase a date with him is the object of the preposition on, while the pronoun him is the object of the preposition with.
Prepositional objects usually immediately follow their prepositions, but there are exceptions. For example, a preposition sometimes comes at the end of a clause:
This is the book I was talking about.
Here, the object of the preposition about is the book.
If you’re ever having trouble identifying the object of a preposition, try rephrasing the sentence to make it more straightforward—for example:
I was talking about this book.
Here, it’s obvious that this book is the object of about.
When a pronoun is a prepositional object, it needs to be in the objective case. So, for example, this is incorrect:
Mum found out about he and I.
He and I are nominative pronouns. The correct version of this sentence would be,
Mum found out about him and me.
Many prepositions also function as adverbs. To identify a preposition, look for a prepositional object. If there is no object, it’s likely an adverb (e.g., around in Birds fly around).
Lean writing should use as few prepositions as possible. One per sentence is usually enough. Sentences with two prepositions can sometimes be reworded—for example:
As he was giving the book to me, he seemed reluctant to hand it over.
This could be reworded as,
As he was giving me the book, he seemed reluctant to hand it over.
Other prepositional phrases can be replaced with adverbs:
The doctor entered in a hurry.
The doctor entered hurriedly.
Some can be eliminated with possessive nouns:
I was confused by the plot of the movie.
I was confused by the movie’s plot.
Some can be eliminated by changing the sentence from passive to active voice:
The cat was brought to the shelter by an old man.
An old man brought the cat to the shelter.
And some prepositional phrases can be completely removed, especially when surrounding text provides the necessary information:
I just finished Pride and Prejudice. The ending was my favorite part of the book.
I just finished Pride and Prejudice. The ending was my favorite part.
These are all of the prepositions used in English:
aboard, about, above, according to, across, after, against, ahead of, along, alongside, amid, amidst, among, amongst, around, as, as far as, as of, as per, as regards, as well as, aside, aside from, astride, at, athwart, atop, barring, because of, before, behind, below