Prepositional Phrases in English Grammar

How to Discern Prepositions From Conjunctions and Adverbs

Prepositional phrase
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In English grammar, a prepositional phrase is a group of words made up of a preposition (such as to, with, or across), its object (a noun or pronoun), and any of the object's modifiers (an article and/or an adjective). It is only a portion of a sentence and cannot stand on its own as a complete thought. Prepositional phrases often tell where something happened, when it happened, or specify which one. Because of these functions, they're often essential to understanding a sentence.

Key Takeaways: Prepositional Phrases

  • Prepositional phrases are groups of words starting with a preposition.
  • Prepositional phrases often function as modifiers, describing nouns and verbs.
  • Phrases can't stand alone. A prepositional phrase won't contain the subject of a sentence.

Types of Prepositional Phrases

Prepositional phrases can modify nouns, verbs, phrases, and complete clauses. Prepositional phrases can also be embedded inside other prepositional phrases.

Modifying Nouns: Adjectival Phrases

When something modifies a noun or pronoun, it's an adjective, so when a phrase does it, it's an adjectival phrase. These types of phrases often specify which person or thing (what kind, whose). In context, they make clear a distinction between several possibilities.

  • Sheila is the runner with the fastest time.

It's likely there are other runners who are slower, as the sentence is specifying who is the fastest. The phrase is modifying (describing) the noun runner. Adjectival phrases come directly after the noun they modify.

  • The boy with her is her son.

The phrase with her is specifying a certain boy; it's an adjectival phrase. There could be other boys, but the one with her is the one that's being described. The boy is a noun phrase, so the prepositional phrase is an adjective. If we want to make the boy even more specific, we'd further qualify it with an embedded phrase.

  • The boy with her on the tricycle is her son.

Presumably, there's a boy with her that's not her son, so the sentence is specifying which boy with her is her son.

Modifying Verbs: Adverbial Phrases

Adverbs modify verbs, and sometimes the adverb is an entire adverbial phrase. These phrases often describe when, where, why, or how something happened or to what extent.

  • This course is the most difficult in the state.

The prepositional phrase specifies where. There might be other courses that are more difficult in other states, but this one is the most difficult here. Let's say it's just one difficult course of several in the state, i.e., "This course is among the most difficult in the state." The among phrase is an adjectival phrase modifying (describing) the course, and the final phrase remains adverbial, still telling where.

  • She ran the marathon with pride on Saturday.

The first prepositional phrase specifies how she ran (a verb), and the second specifies when. Both are adverbial phrases.

List of Prepositions

Here are some of the most commonly used prepositions in English. Be aware that just because a word in a sentence is on this list doesn't mean that it's being used as a preposition in any particular context. Many of these words can also be other parts of speech, such as adverbs or subordinating conjunctions. 

  • about
  • behind
  • except
  • outside
  • above
  • below
  • for
  • over
  • across
  • beneath
  • from
  • past
  • after
  • beside
  • in
  • through
  • against
  • between
  • inside
  • to
  • along
  • beyond
  • into
  • under
  • among
  • by
  • near
  • until
  • around
  • despite
  • of
  • up
  • at
  • down
  • off
  • with
  • before
  • during
  • on
  • without 

Preposition, Conjunction, or Adverb?

To tell if a word is a preposition, look to see if it has an object. If there's a clause following it, you're likely dealing with a conjunction. If it's at the end of a clause instead of the beginning (or the end of a sentence), it's likely an adverb.

After

  • In this example, there is no object following after, and the word introduces a clause, so it's clear that after is a conjunction: After we ate, we went to the theater.
  • In this example, there is an object following after, which means it is used as a preposition: After lunch, we went to the game.

Before

  • In this example, there is an object following before, which means it is used as a preposition: You've put the cart before the horse.
  • In this example, there is no object following before; it is being used as an adverb: I've heard that somewhere before.
  • In this example, there is no object following before and the word introduces a clause, so it's clear that before is a conjunction: Come over before you leave.

Out

  • In this example, there is an object following out, which means it is used as a preposition: The cat followed the child out the door.
  • In this example, there is no object following out; it is being used as an adverb: Would you like to go out for lunch?

When these words are part of a verb phrase, they're adverbs. You check out, look up, and call off something, so these words might appear to be prepositions with objects. But they can't be split off from their verbs.

  • He checked out the book.

Out the book is not a prepositional phrase, as you don't go out a book.

Examining Your Writing

If your writing often contains really long sentences, look at prepositional phrases as a place to cut the chaff or reorganize when revising. Too many of them in a sentence can make it difficult to understand if the sentence gets over 25–30 words or so, depending on how far apart the subject is from its verb. This issue can often be fixed by splitting a long sentence into two or three shorter sentences or moving the verb closer to its subject.