A prepositional phrase is a fixed group of words that functions as a single preposition. It serves to connect two parts of the sentence and indicate a relationship between them: place, time, cause, purpose, accompaniment, opposition, or another similar relation. If removed, the phrase loses that precise connection. In traveled for work, for work expresses the reason for the trip; in is in front of the door, in front of marks the spatial relation. As with the Preposiciones, its role is to introduce and relate, not to name objects or actions.

Fixed Structure and Invariable Form

Idea
The prepositional locution is a fixed unit and does not change its internal words.
It tends to end in a preposition such as a or de.
It functions as a single preposition within the sentence.

The prepositional locution cannot be constructed freely. Its words stay together in a fixed order and do not allow internal changes as other expressions do. It is learned as a complete block: in spite of, beside, under, above. Many end with a simple preposition like to, of, with, for or to, but that last word does not function alone; the whole sequence forms a unit. Therefore you cannot alter the order or substitute a word without changing the expression. In a causa de la lluvia, you do not say causa a de nor a causa para. The full form is what conveys the sense.

Complements that the Locution Follows

Usage	Explanation
Noun	Used before a noun when the locution needs to name the relation clearly.
Pronoun	Used before a pronoun when the locution connects two ideas without repeating the name.
Infinitive	Used before an infinitive when the locution presents an action as a complement.

After the locution the complement that completes the relation appears: a noun, a pronoun, or an infinitive. The locution always comes before that complement and is not placed after. It is said inside the box, beside me, before leaving. When the complement is a pronoun, it usually appears in the tonic form: with me, for you, according to them. With an infinitive, the locution links the action with the idea of time, cause, or purpose, as in without saying anything or before arriving. In the general structure, the sequence is locution + complement, just like in other Common Prepositions that introduce complementary information.

DirecciónAproximaciónConcesiónTiempoLugarModoFinalidadCausa

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Expresa una dificultad que no impide el resultadoExpresa la manera en que se hace algoExpresa una cantidad o medida cercanaExpresa el motivo de una acción o estadoExpresa hacia dónde se mueve alguien o algoExpresa el objetivo de una acciónExpresa dónde sucede algo o dónde queda algoExpresa cuándo ocurre algo

Semantic Values of the Locutions

Word	Definition
Lugar	Expresses where something happens or where something is located.
Tiempo	Expresses when something occurs.
Causa	Expresses the reason for an action or state.
Finalidad	Expresses the objective of an action.
Modo	Expresses the way in which something is done.
Aproximación	Expresses an approximate quantity or measure.
Concesión	Expresses a difficulty that does not prevent the result.
Dirección	Expresses toward where someone or something moves.

Scramble

Many prepositional phrases express place, such as in front of the house, beside the river or on top of the cabinet. Others mark time, such as after dinner or before sleeping. They can also indicate cause: because of the snow, due to a mistake; purpose: with the aim of studying, to save money; and manner: in the form of, with the help of, by means of. The value depends on the relation the locution establishes between the complement and the rest of the sentence. In Place Prepositions, Time Prepositions and Direction Prepositions these senses appear in more detail, because many locutions belong to those domains.

Very commonly used phrases in context

Usage	Explanation
In spite of	It is used to indicate concession and to present an obstacle that does not change the outcome.
Next to	It is used to indicate physical or figurative proximity.
In front of	It is used to indicate earlier position relative to something.
Instead of	It is used to indicate substitution or an alternative.
Under	It is used to indicate lower position.
Behind	It is used to indicate posterior position.
Through	It is used to indicate passage through a medium or space.

Some locutions appear constantly in texts and conversations. In spite of introduces contrast: in spite of the rain, we go out. Beside indicates proximity: the station is beside the park. In front of indicates anterior position: the car is in front of the store. They are also very common under, above, in the middle of, instead of and instead of. Each functions as a single unit and expresses a complete relationship, not just the sum of its words. In reading and listening, recognizing these forms helps to interpret the exact relation between the elements of the sentence, just as happens with the Place Prepositions and everyday expressions.

sobreencima dea pora través de

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Se prefiere en registros claros y cuidados para indicar paso o medioSe usa mucho en el habla cotidiana para expresar posición superiorSe usa de forma neutral y formal para indicar relación o temaSe usa de forma coloquial en algunas zonas para expresar búsqueda o recogida

Usage and register variants

Region	Variant	Definition	Example
Spain	a por	It is used colloquially in some areas to express searching for or picking something up.	Voy a por el pastel que se ha escondido.I am going to get the cake that has hidden itself.
Spain	encima de	It is used often in everyday speech to express superior position.	Puso la taza encima de la radio.He put the cup on top of the radio.
Mexico	sobre	It is used in a neutral and formal way to indicate a relationship or topic.	Hablamos sobre el gato astronauta toda la tarde.We talked about the astronaut cat all afternoon.
Río de la Plata	a través de	It is preferred in clear and careful registers to indicate passage or means.	Llegó a través de una nota escrita en una galleta.He arrived through a note written on a cookie.

Scramble

Some locutions have variants depending on the region or register. In informal speech you may hear a shorter form, but the full version remains the standard written one: a causa de is not reduced in standard, although in conversation shorter equivalent expressions appear. There are also similar locutions that do not mean the same, and it is advisable to distinguish them by the full sense. Gracias a expresses favorable cause, while a causa de presents a normally negative cause. Delante de and frente a can coincide in position, but frente a also introduces opposition or contrast in some contexts. Encima de indicates physical place, while además de adds information. To read them correctly, the relation they create matters, not just the final word.