What is Conversion?

The definition of conversion is controversial, and it has been applied in a number of ways. It also refers typically to the major word classes, especially to nouns and verbs because those are the most frequent patterns, whether from noun to verb or from verb to noun. It is however relevant to have a look at what happens in other word classes, so often neglected in this regard. This paper considers conversion in the light of the categories adverb and preposition, and underlines the difficulty in dealing with these cases in the framework of the most widespread interpretations. In doing so, it evidences the need for a better theoretical apparatus in yet one more regard.