der Alarm
alarm
An acoustic or visual signal that warns of immediate danger.
Plötzlich ertönte der Feueralarm im ganzen Gebäude.
Suddenly, the fire alarm sounded throughout the whole building.

alarm
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alarm
An acoustic or visual signal that warns of immediate danger.
Plötzlich ertönte der Feueralarm im ganzen Gebäude.
Suddenly, the fire alarm sounded throughout the whole building.

'Alarm' is often used in fixed compounds to specify the type of danger. Common ones are 'Feueralarm' (fire alarm), 'Einbruchsalarm' (burglar alarm), or 'Fehlalarm' (false alarm).
Mitten in der Nacht gab es einen Fehlalarm.
In the middle of the night, there was a false alarm.
An alarm is 'ausgelöst' (triggered). When it starts, it 'geht los' (goes off) or 'ertönt' (sounds). These verbs are very typical in connection with a warning signal.
Durch den Rauch in der Küche wurde der Alarm ausgelöst.
The smoke in the kitchen triggered the alarm.
The expression 'Alarm schlagen' (to raise the alarm) is a fixed combination. It means that someone actively draws attention to a danger or a major problem.
Ärzte schlagen wegen der Zunahme von psychischen Erkrankungen Alarm.
Doctors are raising the alarm about the increase in mental illnesses.
warning
'die Warnung' and 'der Alarm' both have to do with danger. A warning is a notice that says: It could become dangerous, or there could be a problem. An alarm is usually a signal, for example a loud sound or a light, and indicates immediate danger. Learners may confuse the words because an alarm also warns you. As a practical rule: You can read or hear a warning, often before the danger occurs. An alarm usually happens suddenly and requires a quick reaction.

Nach der Arbeit hörten wir im Hausflur den Alarm.
After work, we heard the alarm in the hallway.
Die Warnung vor starkem Regen kam schon am Morgen aufs Handy.
The warning about heavy rain arrived on the phone in the morning.