When I was in high school,
I thought that prepositions were just single-worded part of speech that is why
they are really dangerous especially in academic writing. I found out that
there were some kind called "complex prepositions" that were not
single-worded one. Complex prepositions are a word group that functions as a
single preposition that may be two-word or three-word.
Some examples are:
In addition to single-word preposition, there are others called complex preposition.
She is a great composer as well as a great Musical Director.
There are garbage in front of the door.