Prepositions have important general characteristics, knowledge of which can prevent grammar errors
INDIVIDUAL PREPOSITIONS VERSUS PREPOSITIONS IN GENERAL
Prepositions come up regularly in these pages, but the focus is usually on particular ones rather than prepositions in general (clicking on “prepositions” in the CATEGORIES menu on the right of this page will bring up such posts as 31. Prepositions after Action Nouns 1, 72. Causal Prepositions, 73. Ways of Saying How and 111. Words with their Own Preposition).
Nevertheless, it is soon clear from these posts that prepositions have a sizeable number of interesting similarities between them, which we might call general preposition characteristics. Here I wish to highlight seven of the more important of these characteristics, in the belief that their appreciation might help some grammar errors to be avoided.
LIST OF GENERAL PREPOSITION CHARACTERISTICS
1. Need for a Noun-like Partner
Prepositions are like adjectives: they usually partner a noun or noun equivalent. One way to distinguish prepositions from adjectives is by their position relative to a partner noun with the: prepositions go before both words (ACROSS the Nile), adjectives go in between (the BLUE Nile). One interesting word in this respect is worth, which at first sight seems to be an adjective but is clearly a preposition in expressions like worth the effort (see 165. Confusions of Similar Structures 2).
Prepositions can sometimes come after their partner noun instead of before, for example when there is an informal use of who/which/that, like this:
(a) A noun will usually follow the preposition that it depends on.
The formal equivalent of this is, of course, … on which it depends.
The partner word that in (a) is a pronoun rather than a noun. Other noun substitutes include verbs with -ing (see 70. Gerunds), lone adjectives with the, e.g. by the poor (see 6. Adjectives with no Noun 1: People-Naming), some other lone adjectives, e.g. in full, at best (see 85. Preposition Phrases and Corresponding Adverbs and 164. Fixed Preposition Phrases), and small adverbs of time or place, e.g. for now, from here. Even ordinary statements with a subject and verb can follow a preposition if they have the right “joining device”, such as a question word (see 57. Indirect Questions in Formal Writing) or the fact that (see 153. Conjunction Uses of “that”).
If you come across a word that you think is a preposition, but you cannot find a partner noun, then the word may not be a preposition at all. It might instead be a preposition-like adverb of the kind found in two-word verbs (e.g. drop out) and in a special use after BE (e.g. the time is up). For details, see 139. Phrasal Verbs and 154. Lone Prepositions after BE.
2. Creation of Adjective or Adverb Phrases
A preposition and its partner word(s) together act like either an adjective or an adverb. In the adjective-like use, there must be another noun nearby, usually in front, whose meaning the phrase is refining, like travel in this sentence:
(b) Travel BY TRAIN is becoming increasingly popular.
Adverb-like preposition phrases, by contrast, have the same variability as adverbs (see 120. Six Things to Know about Adverbs), being linkable especially with verbs (e.g. went by train), preceding adjectives (e.g. happy with the situation) and whole sentences (see 121. Sentence-Spanning Adverbs). In many cases there is a corresponding ordinary adverb of similar meaning and even spelling (see 85. Preposition Phrases & Corresponding Adverbs). Prepositions at the start of a sentence nearly always make adverb-like phrases (usually with a comma after them):
(c) ACCORDING TO PLATO, the soul belongs to an ideal world of perfect forms.
The ability of preposition phrases to be used like either adjectives or adverbs sometimes creates alternative possible interpretations. A common one is when the phrase comes between a noun and the end of the sentence (see 124. Structures with a Double Meaning). In the following example, who had the stick?
(d) The robbers hit the old man WITH A STICK.
If with a stick is adjectival, its noun is the old man, meaning that he had the stick. However, if with a stick is adverbial (saying something about the verb hit), the stick must have belonged to the robbers. Readers normally decide whether a use is adjectival or adverbial on the basis of which makes the best sense according to the surrounding sentences or their knowledge of the world. Sometimes this needs careful thought, though: the post 3. Multi-Use Words mentions a sentence with from that one learner reported as confusing.
3. Ability to be Multi-Word
Sentence (c) has the two-word preposition according to. Prepositions of two, three or even four words are quite common. In all cases, however, the last word will be a familiar shorter preposition like to. Other examples of multi-word prepositions are in terms of, on the basis of, depending on, in relation to, because of, courtesy of, on account of, due to, thanks to, on (the) top of, in addition to, apart from, instead of, prior to, subsequent to, by means of and in front of.
Also noteworthy is the existence of a few “compound” prepositions (formed by joining separate words into one – see 26. One Word or Two?), for example, throughout, without, upon and into.
4. Similarity to Conjunctions
Prepositions are easily confused with conjunctions. This is because they can often express the same kind of meaning – they differ more in their grammar than their meaning. Compare:
(e) (PREPOSITION) Car use grew during the 20th century.
(f) (CONJUNCTION) Car use grew as the 20th century progressed.
The key difference here is the verb progressed in (f). It is needed mainly because conjunctions, like as, nearly always need a following verb that is not the only verb in the sentence (the other verb here is grew). Conjunctions are considered at length in the post 25. Conjunction Positioning. If the conjunction is changed to the similar-meaning preposition during, no verb is possible.
The similarity between prepositions and conjunctions is reflected in the fact that some prepositions and related conjunctions have the same spelling. The main ones are after, as, before, since and until:
(g) (PREPOSITION) Uganda was ruled by Britain until its independence in the 1960s.
(h) (CONJUNCTION) Uganda was ruled by Britain until it achieved independence in the 1960s.
5. Inability to Go Before the Subject or Object of a Sentence
A noun directly after a preposition cannot usually be the subject or object of a sentence (see 8. Object-Dropping Errors and 12. Singular and Plural Verb Choices). This means that the following sentences are all ungrammatical:
(i) *By working hard brings success.
(j) *In London is cool in summer.
(k) *Near the station means commuting is easy.
The first two here are easily corrected by removing the preposition. An alternative correction in (j) is to add a new noun or pronoun that can serve as the subject, such as the weather or it. Addition is also the way to correct (k) – e.g. living – though here it can only be before the preposition phrase.
Object nouns are usually bound by the same preposition rule, but an important exception occurs when the preposition is part of a two-word “prepositional” verb like DEPEND ON (see next section). Slightly different are “indirect” objects, which can be used either with or without a preposition (see 126. Verbs with an Indirect Object).
6. Ability to Form Prepositional Verbs
Prepositional verbs comprise a verb and a preposition, with or without a noun in between. The preposition is considered to be part of the verb rather than the beginning of a subsequent preposition phrase. Compare:
(l) (PREPOSITONAL VERB) Plants depend on sunlight.
(m) (VERB + PREPOSITION) Plants thrive in well-watered soil.
Prepositional verbs also have to be distinguished from “phrasal” verbs such as SWITCH ON, which contain an adverb instead of a preposition. Phrasal verbs can place their adverb after a following object noun as well as before it: we can say either switch on the light or switch the light on. Further examples of prepositional verbs are in the posts 42. Unnecessary Prepositions, 44. Troublesome Prepositional Verbs, 108. Formal and Informal Words and 123. Prepositional Verbs Containing a Noun.
7. Importance in Both Grammar & Vocabulary
Prepositions tend to be thought of as a part of grammar, in the way that conjunctions and pronouns are, whereas in reality many are best classified as vocabulary instead. Some of their important grammar uses are by and of respectively with the subjects and objects of “action” nouns (see 31. Prepositions after Action Nouns 1 and 49. Prepositions after Action Nouns 2), by after passive verbs, for before some purpose nouns (see 60. Purpose Sentences with “for”), with before an instrument (see 73. Ways of Saying How), and because of to introduce a reason (see 72. Causal Prepositions).
When a preposition use is vocabulary-like, it is often necessitated by the presence of a particular other word, whose dictionary entry it appears in. The other word might be a verb (thus creating a “prepositional” verb), a preceding adjective, a preceding noun (see 78. Infinitive versus Preposition after Nouns and 160. Uses of “of”), or a following noun (see 111. Words with their Own Preposition).
Another vocabulary-like use is in places that allow various alternative preposition meanings. This often happens, for example, when a preposition expresses a basic meaning of place, direction or time – as in to the south (see 151. Ways of Using Compass Words), where in, into, near, from, etc. are also possible, and on Friday, which also allows by, before, after, etc. Resembling these are prepositions of a more metaphorical kind, such as behind meaning “causing” and under meaning “ruled by” (see 7. Metaphorical Meanings).