Adverbs and prepositions often form a continuum in Germanic languages, in the way that the same words might belong to both categories, and to the intermediate category of the prepositional adverb (as part of a phrasal verb or a pronominal adverb) and to that of the postposition, e.g. Dutch ‘de melk is op’, ‘op het bord’, ‘opeten’, ‘daarop’ and ‘de boer op’. In some cases this continuum concerns two different lexemes, as does the one involving Dutch ‘af’ and ‘van’, e.g. ‘het werk is af’, ‘van de week’, ‘aftasten’, ‘eraf’/’ervan’ and ‘het rijtje af’. In this article I will argue that they form their own part-of-speech type category, and I will call them ‘locative adverbia-adpositiones’ (LAA). I will further specify how ‘af’ and ‘van’ relate to each other in Modern Standard Dutch, referring to the equivalent forms in English and in German especially. Finally, I will compare this to Middle Dutch and to modern Dutch dialects.
In the past, ‘van’ has gradually been taking over some of the above-mentioned positions, slightly to the detriment of ‘af’. Data from the nineteenth century, however, shows that ‘af’ has retained its grip in some dialects for much longer than in others.