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"Preposiciones" is a form of "preposición", a noun which is often translated as "preposition". "Variar" is a transitive verb which is often translated as "to alter". Learn more about the difference between "variar" and "preposiciones" below.
variar(
bah
-
ryahr
)A transitive verb is a verb that requires a direct object (e.g., I bought a book.).
1. (to modify)
a. to vary 
Varía los ejercicios que haces para que trabajen todos los músculos.Vary your workout routine to make sure you exercise all your muscles.
An intransitive verb is one that does not require a direct object (e.g., The man sneezed.).
variarse
A pronominal verb always uses a reflexive pronoun. (e.g., Te ves cansado.).
5. (colloquial) (to flaunt) (River Plate)
A word or phrase that is commonly used in conversational speech (e.g., skinny, grandma).
a. to show off 
Se enteró de que los medios cubrirían el evento, entonces fue para variarse.He heard the media would be covering the event, so he went there to show off.
b. to be seen 
Fue a la ópera para variarse, no porque le gusta Wagner.She went to the opera to be seen, not because she likes Wagner.
la preposición(
preh
-
poh
-
see
-
syohn
)A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (grammar)
a. preposition 
En la frase "estoy loco por ti" la preposición es la palabra "por".In the phrase "I am crazy for you," the preposition is the word "for".