A preposition is one of the eight parts of speech in the English language and can come in simple or compound form. Prepositions and compound prepositions are used in everyday written and spoken communications to show relationships between objects and other words in the sentence. Prepositions can also modify verbs to show a relationship between actions or states of being and objects or persons.

Simple Prepositions

To understand compound prepositions, you must first have a clear understanding of simple prepositions. A preposition is a word that is used to connect a noun or pronoun to another word in a complete sentence. This connection shows the relation between the noun or pronoun to the other word in the sentence. Prepositions often show a directional, location- or time-oriented relationship. They can also show exclusion. Some examples of prepositions include "above," "before," "by," "under" and "except." An example sentence: "The cat slept under the coffee table," the word "under" being the preposition.

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Compound Prepositions

Compound prepositions are prepositions that are composed of two or more words. They are used in the same way that simple prepositions are used to show a relationship between a noun or pronoun and another word in the same sentence. Some examples of compound prepositions include "in between," "instead of," "in front of" and "out of." An example sentence: "The cat leapt out of the brown box," "out of" being the compound preposition.

Compound Preposition Usage

Compound prepositions have specific combinations for certain prepositions, and those combinations can be difficult to remember because our ears are not trained to hear the difference between correct and incorrect combinations when spoken aloud. Some commonly incorrect combinations include "apologize about," "bored of," "in search for" and "similar with." The correct forms are "apologize for," "bored with," "in search of" and "similar to." Understanding the correct combinations may be especially difficult for individuals who speak English as a second language. Confusion can be lessened by studying common English idioms, by practice and by carrying a dictionary at all times.

Simple Preposition Usage

Prepositions and compound prepositions remain constant and do not change form according to the case or gender of the word to which they are related. Some rules about using prepositions are especially important. One rule is that the word "of" should never be used directly after the word "off." When indicating location, use the word "between" when speaking about two people or things. In the case of three or more people, use the preposition "among." Simple prepositions are not used when talking about home, downtown, inside, outside, downstairs or upstairs. For example, you would not say, "I am going to home" but "I am going home."