The prepositions formed by prefixing/suffixing a simple preposition to a noun, an adjective or an adverb are called Compound Prepositions.
- There is a long bridge across the river.
- She quit the job against my advice.
- His strange behaviour is beyond my comprehension
- There can be no life without water.
- Who were you talking about that day?
The highlighted words in the above sentences (across, against, beyond, without, and about) are, by definition, compound prepositions.