der Urgroßvater
great-grandfather
The father of one's grandfather or grandmother.
Mein Urgroßvater wurde 1890 geboren und hat zwei Weltkriege erlebt.
My great-grandfather was born in 1890 and lived through two world wars.

great-grandfather
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great-grandfather
The father of one's grandfather or grandmother.
Mein Urgroßvater wurde 1890 geboren und hat zwei Weltkriege erlebt.
My great-grandfather was born in 1890 and lived through two world wars.

The word is made up of the prefix 'Ur-' and 'Großvater' (grandfather). The prefix 'Ur-' here means 'one generation earlier' and is used for ancestors.
Der Urgroßvater meiner Freundin kommt aus Italien.
My friend's great-grandfather comes from Italy.
The prefix 'Ur-' is used systematically for older generations and their descendants. So there is also 'Urgroßmutter' (great-grandmother), 'Urgroßeltern' (great-grandparents), and 'Urenkel' (great-grandchildren; children of the grandchildren).
Meine Urgroßmutter hat über zehn Urenkel.
My great-grandmother has more than ten great-grandchildren.
To specify which side of the family the great-grandfather comes from, you use the additions 'väterlicherseits' (on the father's side) or 'mütterlicherseits' (on the mother's side).
Mein Urgroßvater väterlicherseits war Landwirt.
My great-grandfather on my father's side was a farmer.
grandfather
'der Großvater' and 'der Urgroßvater' both describe male ancestors in the family. The difference is the generation. The grandfather is the father of your mother or father. The great-grandfather is one generation older: he is the father of your grandfather or grandmother. Learners may confuse the words because both have to do with 'Großvater'. Here, 'Ur-' shows: one generation further back.

In der Familie erzählt man oft von dem Urgroßvater, der aus Polen kam.
In the family, people often talk about the great-grandfather who came from Poland.
Sie besucht heute ihren Großvater, weil er Hilfe beim Arzttermin braucht.
She is visiting her grandfather today because he needs help with a doctor's appointment.