der Prinz
prince
A male member of a royal or princely family, especially the son of a king or queen.
Der junge Prinz wird eines Tages den Thron erben.
The young prince will inherit the throne one day.

prince
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prince
A male member of a royal or princely family, especially the son of a king or queen.
Der junge Prinz wird eines Tages den Thron erben.
The young prince will inherit the throne one day.

'Prinz' (prince) is a weak masculine noun (N-declension). This means it takes the ending '-en' in the genitive, dative, and accusative singular.
Die Königin spricht mit dem Prinzen.
The queen is speaking with the prince.
To name the origin or title of a real prince, the preposition 'von' (of/from) is often used, followed by a place or family name.
Prinz Charles wurde später König Charles III. von Großbritannien.
Prince Charles later became King Charles III of Great Britain.
For the idealized figure from fairy tales, the compound word 'der Märchenprinz' (the fairy-tale prince) is used very often. It describes a perfect, heroic man.
In vielen Geschichten rettet der Märchenprinz die Prinzessin.
In many stories, the fairy-tale prince rescues the princess.
duke
'der Prinz' and 'der Herzog' both belong to the world of nobility and monarchy. A 'Prinz' is usually a male member of a royal family, often the son of a king or queen. In fairy tales, the prince is also a typical character. A 'Herzog', on the other hand, is a specific high noble title and can be the ruler of a duchy. Learners may confuse the words because both refer to noble men. 'Prinz' fits when talking about a royal family or fairy tales. 'Herzog' fits when the exact title or a historical territory is meant.

Im Märchen rettet der Prinz das Königreich vor großer Gefahr.
In the fairy tale, the prince saves the kingdom from great danger.
Der Herzog lebte früher in einem Schloss am Fluss.
The duke once lived in a castle by the river.