der Urenkel
great-grandson
The son of a grandchild; a male descendant in the third generation after a person.
Mein Großvater ist 95 Jahre alt und hat bereits drei Urenkel.
My grandfather is 95 years old and already has three great-grandsons.

great-grandson
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great-grandson
The son of a grandchild; a male descendant in the third generation after a person.
Mein Großvater ist 95 Jahre alt und hat bereits drei Urenkel.
My grandfather is 95 years old and already has three great-grandsons.

The prefix 'Ur-' is used with family terms to go one generation further. An 'Enkel' (grandchild) is the child of one's child; a 'Urenkel' (great-grandson) is the child of one's grandchild.
Wenn mein Sohn ein Kind bekommt, werde ich Großvater. Wenn mein Enkel ein Kind bekommt, werde ich Urgroßvater.
When my son has a child, I will become a grandfather. When my grandson has a child, I will become a great-grandfather.
The system with 'Ur-' works in both directions of the sequence of generations: Urgroßeltern (great-grandparents) → Großeltern (grandparents) → Eltern (parents) → Kinder (children) → Enkel (grandchildren) → Urenkel (great-grandsons).
Meine Urgroßmutter hat ihre Urenkel noch kennengelernt.
My great-grandmother still got to meet her great-grandsons.
Common verbs used with 'Urenkel' (great-grandson) are 'haben' (to have) or phrases like 'stolz sein auf' (to be proud of) one's great-grandsons.
Die alte Dame ist sehr stolz auf ihre fünf Urenkel.
The old lady is very proud of her five great-grandsons.
grandson
'der Enkel' and 'der Urenkel' both belong to male descendants in the family. However, they differ in generation. The grandson is the son of one's own child. The great-grandson is the son of a grandchild, so one generation further. The words can be confused because they sound similar and both express a relationship to grandparents. A practical way to remember it is: child, grandson, great-grandson — each step goes one generation further.

Am Montag besucht der Urenkel seine Urgroßmutter im Pflegeheim.
On Monday, the great-grandson is visiting his great-grandmother in the nursing home.
Mein Enkel hat mir ein Bild aus der Schule mitgebracht.
My grandson brought me a picture from school.