der Dummkopf
fool
A derogatory term for a person who is considered stupid, unwise, or foolish.
Nur ein Dummkopf würde bei diesem Wetter ohne Jacke nach draußen gehen.
Only a fool would go outside without a jacket in this weather.

fool
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fool
A derogatory term for a person who is considered stupid, unwise, or foolish.
Nur ein Dummkopf würde bei diesem Wetter ohne Jacke nach draußen gehen.
Only a fool would go outside without a jacket in this weather.

The word is made up of the adjective 'dumm' (stupid) and the noun 'Kopf' (head). So it literally describes a person with a 'dummen Kopf' (stupid head).
Er fühlt sich wie ein Dummkopf, weil er die einfache Frage nicht beantworten konnte.
He feels like a fool because he couldn't answer the simple question.
'Dummkopf' (fool) is a strong insult. You should use this word with great caution, as it can be felt to be very hurtful and derogatory.
Schrei mich nicht an und nenn mich nicht Dummkopf!
Don't yell at me and don't call me a fool!
You can directly call someone a 'Dummkopf' (fool), e.g. 'Du bist ein Dummkopf!' (You are a fool!), or comment on a person's action this way, e.g. 'Das macht nur ein Dummkopf.' (Only a fool would do that.).
Sei kein Dummkopf und denk nach, bevor du handelst.
Don't be a fool, and think before you act.
hero
'der Held' and 'der Dummkopf' can both refer to someone who has done something unwise, but only in a special usage. 'der Dummkopf' is a clearly derogatory term for an unwise person. 'der Held' is normally positive, but colloquially it can be meant ironically. In that case, you say 'Held' even though you actually mean that someone acted clumsily or without thinking. 'Dummkopf' is more direct and harsher; the ironic 'Held' often sounds mocking and depends strongly on tone.

Sei kein Dummkopf und gib dein Passwort niemandem weiter.
Don't be a fool and give your password to anyone.
Der Held hat die falsche Tür abgeschlossen und kommt jetzt selbst nicht mehr hinein.
The hero locked the wrong door, and now he can't get back in himself.