der Po
bottom
Colloquial term for the buttocks; the part of the body you sit on.
Das Kind ist beim Spielen auf den Po gefallen.
The child fell on their bottom while playing.

bottom / Po
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bottom
Colloquial term for the buttocks; the part of the body you sit on.
Das Kind ist beim Spielen auf den Po gefallen.
The child fell on their bottom while playing.

The two meanings can only be distinguished by context. If people are talking about geography, Italy, or cities like Turin, the river is meant. If it is about the human body, sitting, or falling down, the buttocks are meant.
Die Po-Ebene ist eine sehr fruchtbare Region in Italien.
The Po Valley is a very fertile region in Italy.
In the meaning 'Gesäß' (buttocks), 'der Po' is a colloquial word. It is often used in everyday speech and when talking with children.
Das Baby hat einen wunden Po.
The baby has a sore bottom.
When the river in Italy is meant, the definite article is almost always used: 'der Po' (the Po). For example, people speak of a trip to the Po.
Der Po ist der längste Fluss Italiens.
The Po is the longest river in Italy.
ass / asshole
'der Arsch' and 'der Po' can both refer to the body part you sit on. 'Po' is mild, everyday language and can also be used in friendly or neutral situations. 'Arsch' is vulgar and sounds crude; you should use it only in very casual speech. Learners may confuse the words because they refer to the same body part. As a practical rule: if you want to speak politely or neutrally, use 'Po'.

Das Kind ist hingefallen und hat jetzt Schmerzen am Po.
The child fell down and now their bottom hurts.
Er rutschte auf dem nassen Boden aus und fiel auf den Arsch.
He slipped on the wet floor and fell on his ass.