Page 145 - Perfect English Grammar: The Indispensable Guide to Excellent Writing and Speaking

Prepositions explain relationships of space, sequence, and logic between the
object of the sentence and the rest of the sentence. They help us understand

connections, positions, order, and time.
Prepositions are linguistically interesting in a few key ways. First, they

represent a closed class, meaning that new prepositions are very rarely added to
the language. We use what we have. Second, prepositions have just one form.

They don’t take a plural (see section 8.6, Plurals), a possessive (see section 8.2,
Possessives), an inflection, or anything else.

Each preposition can have many different uses, and their appearance in

phrasal verbs (which is different than a verb phrase; see section 5.6, Phrases) can
be easy to confuse with regular prepositional use.

In particular, about, at, for, and on are troublesome for those learning
English as an additional language. For one thing, there is usually no perfect one-

to-one correspondence between the prepositions in one language and the
prepositions in another. Where English uses to, another language might use three

other words, or vice versa. For another, even in English there may be regional or
dialect differences.

Prepositions may be one, two, three, or even more words. We can call the

multiword prepositions phrasal prepositions (not to be confused with
prepositional phrases; see section 5.6.3).

There are three main roles for prepositional phrases.

1. They can function as nouns following forms of the verb to be.

Her hat is under her chair.
Water is on Mars.

2. They can function as adverbs modifying verbs, just as ordinary
adverbs do.

We split up without a plan for meeting up again later.
This rope does not break under heavy loads.

3. They can function as adjectives modifying nouns.
The car next to mine was left running.

It rained after my pool party.