Etymologically speaking, we have to determine what preposition is a word that derives from Latin. Specifically, it must be said that it is the result of the sum of two perfectly defined and differentiated components:
-The prefix “pre-”, which can be translated as “before”.
-The term "positio", which derives from the verb "ponere" which is synonymous with "place."
Preposition it's a kind of word that does not vary and that allows to introduce certain elements to a sentence , making these depend on other words already mentioned.
Prepositions are usually found at the beginning of the syntactic constituent to which they modify. By linking words, prepositions function as invariable parts of the sentences that are responsible for denoting the link of the terms with each other.
The Royal Spanish Academy (RAE) recognize 23 prepositions in the Spanish language used today. Among them appear "to", "with", "from", "in", "until", "for", "by", "yes" and "on".
It is important to keep in mind that the different prepositions can come to indicate a great variety of elements. Thus, for example, they can be used to indicate a place, an origin, a motive, a means or even a destination, among many other things.
To understand this, just use the preposition "a". So when used in the phrase "I go to the library", it comes to indicate an address, while if it is used in sentences such as "we are July 6, 2015" makes clear one day.
An example of prayer with preposition is as follows: "I will give a ball to Martin". In this case, the preposition included is "to", which allows to relate the present in question (a ball ) with the recipient of the gift (Martin ).
Another sentence with prepositions is “Raúl will dance with Estela on graduation night”. Among the prepositions that appear, are "with" (which links to Raul and Wake ) and "in" (indicates when the dance from both).
In addition to all of the above, we cannot ignore the existence of what is called inseparable preposition. This denomination refers to that prefix that was once used as a simple preposition and that, at present, can never be used alone. An example of this is "sub."
In the same way, there are also the so-called prepositional phrases. These come to be groups of words that come to work and to mean as if it were a single preposition and, therefore, when it comes to parsing a sentence you have to study them as a unit. Examples of prepositional phrases are "under" or "through."
In some cases, the prepositions link auxiliary verbs with others that appear impersonally, creating what is known as verbal periphrasis : “You have to shout louder”, "I will run when I hear the signal".
Prepositions can cause a contraction with the articles, creating a contract article . This happens when "to" or "from" precede the article "he", leading to the birth of "to the" and "of the": "I will cook the steamed eggs", "Knock on the neighbor's door".