auf meaning and definition in german
Preposition
Frequency: 
- with dative on, upon Das Buch liegt auf dem Tisch. The book is lying on the table.
- with accusative on, onto Leg das Buch auf den Tisch! Put the book on the table!
- colloquial, otherwise, archaic, regional, northern and western Germany on (a day; usually of the week) Du kannst doch auf (’n) Sonntag nich’ den Rasen mähen! You can’t mow the lawn on a Sunday!
Adverb
Frequency:
Compare to the latter example the phrase: Die Milch ist aus, which would mean that all the milk has been sold out, e.g. from a supermarket. 