Verbs that rely on one or more prepositions (or adverbs) for different, and mostly idiomatic, meanings (you couldn't guess the from knowing both words, as, for example 'look out for') are called 'phrasal' verbs. They can have one or two 'particles (prepositions or adverbs) following them, so are sometimes called two-word verbs, or three-word verbs, and are separable, or inseperable. Many grammars do not bother to say why - the explanation is that when followed by a preposition only, they can be separated- for example 'look up', where 'up' is an adverb it can be used both ways 'look the word up /look up the word', when it is a preposition, it has to be attached to an object 'look for my keys', NOT 'look my keys for'. Of course, there are also many verbs that have prepositional prefixes, as in the translation 'overcome' (the darkness.) In addition, there are nouns with particle prefixes and suffixes ('lookout', 'takeover' etc.) many of which can be used as adjectives also - lookout post/takeover bid) Is this true of Greek?