der Donner
thunder
The loud, rumbling sound that follows a flash of lightning during a thunderstorm.
Erst sahen wir den Blitz, dann hörten wir den lauten Donner.
First we saw the lightning, then we heard the loud thunder.

thunder
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thunder
The loud, rumbling sound that follows a flash of lightning during a thunderstorm.
Erst sahen wir den Blitz, dann hörten wir den lauten Donner.
First we saw the lightning, then we heard the loud thunder.

The word 'Donnerwetter!' is a well-known exclamation. It can express surprise, annoyance, or admiring amazement, similar to 'Wow!' or 'Good heavens!'.
Donnerwetter, das hast du aber schnell geschafft!
Wow, you managed that quickly!
'Donner' (thunder) almost always appears together with 'Blitz' (lightning), often in the fixed combination 'Blitz und Donner' (thunder and lightning). A typical verb that describes the sound is 'grollen' (to rumble).
Bei dem Gewitter gab es die ganze Nacht Blitz und Donner.
During the thunderstorm there was thunder and lightning all night.
In this figurative meaning, the source of the loud sound is often named directly. Typical compounds are 'Kanonendonner' (cannon thunder) or 'Applausdonner' (thunderous applause).
Nach der Rede erfüllte lauter Applausdonner den Saal.
After the speech, thunderous applause filled the hall.
bang
'der Knall' and 'der Donner' both describe loud noises. A 'Knall' is usually short, sudden, and sharp, for example when something bursts or explodes. 'Donner' is more deep, rumbling, and longer; it is typical in a thunderstorm, but a similar booming sound can also be called this. The words can be confused because both are loud. If the sound is like a short hit or bang, 'Knall' fits better. If it rumbles or sounds like a thunderstorm, 'Donner' is more natural.

Beim Frühstück hörte Frau Richter den Donner und schloss schnell das Fenster.
During breakfast, Mrs. Richter heard the thunder and quickly closed the window.
Plötzlich gab es einen lauten Knall, und der Ballon war kaputt.
Suddenly there was a loud bang, and the balloon was broken.