
der Ernstfall
emergency
A real, serious, and often dangerous situation, as opposed to a drill, test, or theoretical assumption.
Die Feuerwehr probt regelmäßig für den Ernstfall.
The fire department regularly drills for an emergency.
emergency
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emergency
A real, serious, and often dangerous situation, as opposed to a drill, test, or theoretical assumption.
Die Feuerwehr probt regelmäßig für den Ernstfall.
The fire department regularly drills for an emergency.

in an emergency
A fixed expression meaning “in a real emergency” or “when things really become serious.”
Im Ernstfall müssen Sie diese Notrufnummer wählen.
In an emergency, you must call this emergency number.
'Der Ernstfall' (emergency) is made up of the adjective 'ernst' (serious) and the noun 'der Fall' (case). So it literally describes a “serious case” or a serious situation.
Wir müssen auf einen Ernstfall vorbereitet sein.
We have to be prepared for an emergency.
This noun is often used with certain verbs that describe preparation or an occurrence. Typical phrases are 'für den Ernstfall üben/proben' (to practice/drill for an emergency), 'sich auf den Ernstfall vorbereiten' (to prepare for an emergency), and 'der Ernstfall tritt ein' (the emergency occurs).
Die Rettungskräfte üben regelmäßig für den Ernstfall.
The rescue workers regularly drill for an emergency.
The fixed expression 'im Ernstfall' (in an emergency) functions as an adverbial. When it appears at the beginning of a sentence, the conjugated verb follows directly in second position.
Im Ernstfall müssen alle das Gebäude sofort verlassen.
In an emergency, everyone must leave the building immediately.
emergency
Notfall and Ernstfall both refer to a serious situation, but they are used differently. Notfall is used especially in technical or organizational terms such as Notfallplan, while Ernstfall refers to the real situation as opposed to a drill or theory. Notfall is appropriate for a plan, while Ernstfall is appropriate for what actually happens.

Bei der Übung lernten die Mitarbeitenden, was sie im Ernstfall tun sollen.
During the drill, the employees learned what they should do in a real emergency.
Der Notfallplan erklärt, was die Mitarbeitenden bei einem Brand tun sollen.
The emergency plan explains what the employees should do in the event of a fire.