auf

Auf is a common word in German that functions primarily as a preposition and as a separable prefix in verbs. It also appears in a number of fixed phrases and idioms. The basic sense of the preposition is related to position or direction, often translated as on, onto, or upon, depending on context and case.

As a preposition, auf governs case according to movement or location. With a static location, it takes the dative: for example, auf dem Tisch means on the table. With direction or movement toward a surface, it takes the accusative: auf den Tisch means onto the table. It can also convey other relational meanings, such as contact with a surface or a state of readiness, as in auf dem Weg (on the way) or auf dem Laufenden (up to date).

As a separable prefix, auf attaches to many verbs to indicate completion, initiation, or an upward/spatial sense. In main clauses it often separates: Ich stehe früh auf (I get up early). In perfect or compound tenses the prefix remains with the verb stem: Ich bin früh aufgestanden. Other examples include aufmachen (to open), aufbauen (to set up/build up), and aufhören (to stop). The prefix contributes aspectual shading but the meaning varies with the verb.

Etymologically, auf derives from Old High German uf, related to other Germanic terms for upward or surface contact. In everyday language, auf features prominently in idioms and fixed expressions such as auf jeden Fall (in any case), auf keinen Fall (by no means), and auf dem neuesten Stand (up to date). Its versatility makes it one of German’s most productive particles.