Preposition - a part of speech that indicates a relationship between two or more concepts
Prepositions help the reader to understand where and when something is. They usually refer to nouns, but they can also apply to verbs.
That said, prepositions can be a little fiddly because they're usually small and can be more than one word. However, it is worth knowing how they work alongside other parts of speech.
Consider the following sentence, with a preposition in bold:
Example
The phone is on the desk.
In this sentence, the preposition on connects two noun phrases: the phone and the desk.
Specifically, the preposition tells us where the subject of the sentence (the phone) is in relation to the object (the desk).
Usually, a preposition comes before a noun or pronoun, and we can say that the preposition governs this person or thing. With reference to the example above, we can say that the preposition on governs the noun phrase the desk.
There are many prepositions in English, and it is tricky to categorise them efficiently.
Broadly, we can place them into the following categories:
Category
Direction
Space
Time
Abstract
Prepositions
to, towards, from
under, in front of
since, until, by
of, with
Examples
They're going to the movies.
The remote is under the couch.
I've been working since dawn.
The Greeks rescued Helen of Troy.
Prepositions and the other words that help them to govern a noun or verb are considered prepositional phrases.
Prepositional phrase - a group of one or more words, including a head preposition, which together function as an adjective or adverb.
As with noun phrases, verb phrases, adjective phrases and adverb phrases, a prepositional phrase is considered a single grammatical element within a sentence.
However, prepositional phrases function differently depending on the part of speech they govern.
Specifically, if a prepositional phrase governs a noun or pronoun it functions as an adjective, while if it governs a verb, it functions as an adverb.
Consider the following sentence, which contains a number of prepositional phrases:
Example
Before dawn, we rose from our beds and sauntered down to the beach to watch the morning sun fill the sky above us.
How many prepositional phrases can you spot?
Dramatic music.
I count four:
Before dawn is a prepositional phrase that functions as an adverb to govern the verb rose. It tells the reader when this action took place.
from our beds functions as another adverb to govern the verb rose. It tells the reader about the direction of this action.
down to the beach is an adverb to govern the verb sauntered, telling the reader the direction of this action.
above us is a prepositional phrase that functions as an adjective to govern the noun sky. It tells the reader the location of this thing.
While there is more to prepositions than what we have covered here, for everyday usage this should keep us busy.
That said, if you would like to know more there are other excellent resources available online, including the Purdue University Online Writing Lab (OWL) guide to prepositions.