In grammar, a preposition is a type of adposition, a grammatical particle that establishes a relationship between an object (usually a noun phrase) and some other part of the sentence, often expressing a location in place or time.
Examples (indicating preposition and the prepositional phrase):
- My coat is on the sofa.
- I knitted throughout the day.
- They will not be finished until lunchtime.
- The keys are between the cushions.
- A man hid behind the door
The preposition and its object make up a prepositional phrase, which can be used to modify noun phrases and verb phrases in the manner of adjectives and adverbs. For example, in the sentence "He has a can of lemonade", the prepositional phrase of lemonade is used to modify the noun can. In the sentence "The girl sat in the chair", the prepositional phrase in the chair modifies the verb sat.
Although the canonical object of a preposition is a noun phrase, there are cases in which another kind of phrase forms a prepositions object. For instance, in the sentence "Come out from under the bed", the object of the preposition from is another prepositional phrase, under the bed. Furthermore, according to some analyses, in the sentence "I opened the door before he walked in", before is not a conjunction but rather a preposition whose object is a full sentence (he walked in).
In common speech, the object of a preposition may be implied. For instance, "Get in the car" may be shortened to "Get in."
English prescriptive guidelines
In English usage, prescriptivists often argue that, since prepositions are usually meant to come before the words they modify, one should not end a sentence with a preposition. This guideline stems from the pre-20th century belief that Latin is a perfect language, since it never changes. Latin was the literary language among English speakers in the Middle Ages, and Church Latin remains the language of the Catholic Church to this day. In Latin, prepositions always immediately precede the nouns they modify, thus never appearing at the end of a sentence.
However, the reason why Latin doesn't change is because there are no more native speakers. When Latin was an active language, it changed over time just like any other language. Furthermore, Latin is a heavily inflected language, while Modern English relies primarily on word order to convey grammatical meaning.1 As a result, English has far more prepositions than Latin. Latin does not need as many prepositions because its larger number of cases supplement prepositions in their function of conveying grammatical meaning. These realizations have come relatively recently by descriptive linguistics.
Following this prescriptivist guideline can frequently make a sentence become unnecessarily complicated. For example, compare "The table I'd like to sit at", with "The table at which I'd like to sit". To most English speakers, the former sounds more natural, while the latter sounds stilted and overly formal. "The table where I'd like to sit" is one possible compromise between these two options, and should avoid offending those who prefer sentences not to end in prepositions.
Many other Germanic languages, such as German, employ separable prefix verbs in which a prefix (usually adopted from a preposition) modifies a verb. The prefix frequently appears separate from the verb at the end of the sentence. For instance, "arrive" in German is "ankommen" (literally the word "to" prefixed to the word "come"). A sentence that uses this verb in any form other than as an infinitive, however, will put the "an" at the end of the sentence: "Die Frau kommt um 7 Uhr in Köln an." (Literally: "The woman comes at seven o'clock in Cologne to."; Idiomatically: "The woman arrives in Cologne at seven o'clock.") Some grammarians hold that English prepositions at the ends of sentences are related to this Germanic usage, and therefore natural parts of the English language. But, it should be noted that separable prefixes are not prepositions and do not generally modify or introduce prepositional clauses.
Other relational particles
Some languages, such as Japanese, place relational particles after the noun and thus have what are called postpositions.
In Chinese, certain verbs known as coverbs express many of the relationships usually expressed by prepositions. Because coverbs appear before the noun phrase they modify and essentially function as prepositions, they are often referred to as prepositions, even though they are lexically verbs and can in many cases stand alone as the main verb.
In inflected languages, prepositions are not separate words; their function is instead performed by a system of inflections on nouns called case or declension. Many linguists consider prepositions and postpositions, like inflectional particles, to all mark case. Due to this functional similarity, there is a small amount of contention regarding the difference between a case marker and an adposition. Otto Jespersen contends that the difference is purely related to form: agglutinative languages have case markers, while isolating languages have adpositions. In The Philosophy of Language, he states that "[T]here is a fundamental incongruity between the Latin system where the case-distinctions are generally, though not always, expressed in form, and the English system where they are never thus expressed" (178; emphasis original). John Taylor, on the other hand, proposes a definition that restricts case markers to those particles with a nominal profile -- that is, the phrase marked by a case marker can serve as a noun, whereas a phrase marked by an adposition cannot.
- Historically, English was in fact an inflected language, relying on cases instead of word order to convey grammatical information. Thus English had a much smaller number of prepositions in its lexicon. However, as Old English evolved into Middle English into Modern English, inflections were dropped in favor of word order, and many new prepositions were added. See: History of the English language; Declension in English.