Offen vs. geöffnet vs. auf
The German words offen, geöffnet, and auf can all translate to open, but they are not always interchangeable. The difference lies in their grammatical function, formality, and whether they describe a state, the result of an action, or are used colloquially.
Offen
A1This is the most common and versatile adjective for open. It describes the general state of something and can be used for physical objects, abstract concepts, and personality traits.
Bitte lass die Tür offen.
(Please leave the door open.)
Wir müssen über dieses Thema offen sprechen.
(We have to speak openly about this topic.)
Er ist ein sehr offener und ehrlicher Mensch.
(He is a very open and honest person.)
Die Geschäfte sind sonntags nicht offen.
(The shops are not open on Sundays.)
Es gibt noch viele offene Fragen zu klären.
(There are still many open questions to clarify.)
Geöffnet
A2This is the past participle of the verb öffnen (to open) and is used as an adjective. It emphasizes that something has been opened by an action and is often used in more formal or official contexts, especially for business hours.
Das Museum ist von 9 bis 17 Uhr geöffnet.
(The museum is open from 9 am to 5 pm.)
Das neu geöffnete Restaurant ist sehr beliebt.
(The newly opened restaurant is very popular.)
Die Flasche war bereits geöffnet, als ich sie fand.
(The bottle was already opened when I found it.)
Die Schranke wird nur für autorisierte Fahrzeuge geöffnet.
(The barrier is only opened for authorized vehicles.)
Halten Sie das Fenster während der Fahrt bitte nicht geöffnet.
(Please do not keep the window opened while driving.)
Auf
A2This is a colloquial and informal word for open, used almost exclusively in spoken language for physical objects. It functions like an adjective but can only be used after the noun and verb (e.g., Die Tür ist auf). It cannot be used before a noun.
Mach schnell das Fenster auf, es ist heiß hier drin.
(Quickly open the window, it's hot in here.)
Moment, der Reißverschluss von deiner Tasche ist auf.
(Wait, the zipper on your bag is open.)
Ist der Supermarkt noch auf?
(Is the supermarket still open?)
Der Deckel von der Kiste ist auf.
(The lid of the box is open.)
Warum ist die Haustür einfach auf?
(Why is the front door just open?)
Summary
In short: Use offen as the standard, all-purpose word for open for both physical and abstract things. Use geöffnet for a more formal tone, especially for business hours and to emphasize that something was opened by an action. Use auf in casual, spoken German for physical objects when you would say is open.