What Are Prepositions?

Prepositions define relationships between their objects and other words in the sentence. Prepositions describe relationships of time, place, direction, location, introduction and space. In the English language, the most common prepositions are simple words of fewer than 5 letters. Complex prepositions, such as the phrase "in spite of," often develop over time from groups of words commonly used together.

Prepositional phrases function as modifiers of a verb ("walk on water"); modifier of a noun ("wines from California"); complement of a verb ("insist on working alone"); complement of a noun ("an appeal to the court"); complement of an adjective or adverb ("disrespectful to their teacher"); and complement of another preposition ("out of the pot into the frying pan").

Prepositional phrases consist of three parts: a simple or complex preposition, the object (noun, pronoun or gerund) and the object modifiers. A preposition sits in front of the noun or pronoun object (pre-positioning) in the simplest sentence constructions. There are about 170 prepositions in the English language, including "since," "above" and "but." The English language word frequency project at wordcount.org lists the ten most frequently used prepositions as: of, to, in, for, on, with, as, by, at, from. Wordcount ranks "of" as the second most frequently used word in English, while "from" ranks twenty-ninth.

Prepositions belong to a linguistic class of modifiers and compliments called adpositions. Prepositions are adpositions placed before the object (noun, pronoun or gerund) in the phrase (pre-positioning). Example: "by the chair"--the preposition "by" appears before the object "chair." Postpositions are modifiers placed after the object of the adpositional phrase. Circumpositions are rare in English, consisting of modifiers placed before and after the object of the adpositional phrase. Example: "from then on"--the circumposition consisting of "from" and "on" surrounds the object "then." Interpositions are adpositions surrounded by the object. Example: "word for word"--the adposition "for" is in the middle of the prepositional phrase structure. Ambipositions are adpositional phrases correctly appearing in either preposition or postposition form. Example: "through the day, the day through." Linguists classify prepositions, postpositions, circumpositions, interpostions and ambipositions as adpositions; but we commonly call all these types prepositions.

Prepositional stranding, or using a preposition without an object, is generally considered improper use in English. Grammar check programs flag sentences ending with a preposition for this reason. Reword to include the object or remove the preposition. Many words used as prepositions also function as adverbs, conjunctions or particles. Identify the object to determine classification as a preposition. Prepositions usage is one of the more challenging aspects of learning a language, resulting in frequent errors and frustration for non-native speakers. Prepositions are a common downfall for TOEFL test takers. Purdue Online Writing Lab offers excellent handouts on preposition usage (see Resources below).

Online Writing Support for Towson University offers a test for whether a word is a preposition or particle (see Resources below). Move the phrase starting with the word to the start of the sentence. If the sentence makes sense starting with the clause, then it is a prepositional phrase. If the sentence no longer makes sense, check to see if the word is actually a particle (a word also used as a preposition that is part of a verb in this application). Examples of particles include: move on, broke up, gave in, came by, wore out, put in for.