During my lessons I see students struggle with the German prepositions ‘an’ and ‘auf’. Both are used to describe locations and require either the Accusative or the Dative case. If we can ask ‘wohin’ (where to), then the preposition requires the Accusative and if we ask ‘wo’ (where) then the Dative is required. This begs the questions why we use cases after prepositions. The answer is simple: on = auf + Dative and onto = auf + Accusative. English uses two different prepositions to describe these two different scenarios, whereby German uses the same preposition but two different cases to describe the same two scenarios. When do you use auf and when do you use an? Auf is always used when something is resting on something else that is horizontal and an is used when something is resting on something that is vertical: auf dem Tisch – on the table (horizontal) but an der Wand – on the wall (vertical). if you would like to refresh your German or start learning German, then get in touch and book one of our private German tutors.